Spread spectrum transceiver module utilizing multiple mode transmission

ABSTRACT

A data transceiver module for digital data communications in a portable handheld data terminal has multiple data spread spectrum modes which include direct sequence and frequency function modulation algorithms. The transceiver module has multiple user or program configurable data rates, modulation, channelization and process gain in order to maximize the performance of radio data transmissions and to maximize interference immunity. Various module housings, which may be PCMCIA type, are able to be mated with a suitably designed data terminal. Media access control protocols and interfaces of multiple nominal operational frequencies are utilized. Wireless access devices in a cell based network each consider a variety of factors when choosing one of a plurality of modes of wireless operation and associated operating parameters. Such selection defines a communication channel to support wireless data, message and communication exchanges. In further embodiments, the wireless access devices also support a second channel, a busy/control channel, for managing communication on the main communication channel and to overcome roaming and hidden terminal problems. Roaming terminal devices are also configured to support the dual channel design. Such configuration in both circumstances may involve the use of a multimode radio that is timeshared between the two channels or two radios, one dedicated to each channel.

BACKGROUND

[0001] 1. Technical Field

[0002] The present invention relates generally to communication networksutilizing spread spectrum radio transceivers, and, more specifically, tomulti-hop RF networks wherein participating devices utilize spreadspectrum transceivers that are capable of operating in any of a varietyof spread spectrum modes. The spread spectrum modes include, forexample, direct sequence transmission across a spreading bandwidth orchannelized across the spreading bandwidth, frequency hoppingtransmission across all or a part of the spreading bandwidth, a hybridcombination of direct sequence transmissions and frequency hoppingtransmissions, and transmissions on a portion of the spreadingbandwidth. The selection of a spread spectrum mode of operation dependsupon signal conditions and characteristics of members capable ofcommunication within the RF communication network.

[0003] 2. Description of Related Art

[0004] Communication devices within a wireless local area network employwireless communication links to transfer data and commands within thelocal area network. Typical units within a wireless local area networkinclude stationary wireless access devices, mobile radio units, mobileimage capture units, printing units, and other units operative with thedata and commands. These units often link to a wired local area networkthrough a wireless access device to transfer data and commands todevices located on the wired network. The wireless local area networkstypically employ cellular communication techniques to provide thewireless communication links within the local are network.

[0005] One common installation of a wireless local area network servesfactory automation functions. Because hard-wiring a local area networkwithin a large, dynamic facility is both expensive and difficult, thewireless local are network provides traditional network functions aswell as additional functions germane to the wireless attributes of thenetwork. However, due to difficult transmission and interferenceconditions within a factory, establishing and maintaining sufficientwireless communication ties oftentimes proves difficult. Attenuation oftransmitted signals, multi-path fading, ambient noise, and interferenceby adjacent cells often disrupts communication within the wireless localarea network.

[0006] Spread spectrum transmissions are often used in attempts toovercome communication problems. With spread spectrum transmissions, thebandwidth over which information is broadcast is deliberately made widerelative to the information bandwidth of the source information. Spreadspectrum transmission techniques include direct sequence transmission,frequency hopping transmission, a combination of direct sequencetransmission and frequency hopping transmission, and may include othertechniques that deliberately transmit over a wide spectrum.

[0007] Direct sequence spread spectrum transmitters typically spread byfirst modulating a data signal with a pseudo random chipping sequence ata multiple of the source data clocking rate. Once constructed, thecomposite modulation is coupled to a carrier via modulation techniquesand then transmitted. Please modulation is typically employed, butfrequency modulation or other types of modulation may also be used.Circuitry in a receiving units receives the signal, decodes the signalat the multiple of the source data clocking rate using a particularchipping sequence, and produces received data. In a typical directsequence system, the pseudo random chipping sequence applied by thereceiving unit corresponds to all, or respective portions, of thetransmitted signal. In this fashion, the receiving unit receives onlyintended data and avoids receiving data from adjacent cells operating onthe same frequency. Direct sequence spread spectrum modes also providesignificant noise rejection characteristics since each component of thesource data is essentially transmitted multiple times. The receivedsignal is therefore a composite that may be averaged or weighted toavoid receiving improper data or falsing based upon noise.

[0008] A frequency hopping system commonly uses conventional narrowbandmodulation but varies the modulation frequency over time in accordancewith a known pattern or algorithm, effectively moving the modulatedsignal over the intended spreading bandwidth. The spread spectrum signalis only discernible to a receiver that has prior knowledge of thespreading function employed and which has obtained synchronization withthe spreading operation at the transmitter. By spreading transmissionsover the spreading bandwidth, particular portions of the spreadingbandwidth within which transmission is difficult may be substantiallyavoided.

[0009] In the United States and many other countries, spread spectrumcommunications is used commercially within designated Industrial,Scientific and Medical (ISM) bands. These bands are structured asmulti-use bands containing non-communications equipment such asindustrial and commercial microwave ovens as well as low power consumergrade transmitters, vehicle location and telemetry systems and otherspread spectrum devices of differing characteristics. Operation in ISMbands is unlicensed and uncoordinated, so equipment operating in thesebands must be designed to operate successfully without knowledge of thetypes of devices that may be used in close proximity. The spreadspectrum system design must also take into consideration the occupantsof the spectrum adjacent to the ISM bands which may be both potentialsources of interference to, and susceptible to interference from,various types of spread spectrum products.

[0010] Various forms of modulation across the spreading band may beutilized in commercial spread spectrum packet data communicationsystems. Full band direct sequence systems occupy the entire width of anISM band. The spreading ratio, the ratio of the bandwidth of the spreadspectrum modulated signal to the information bandwidth of the sourcemodulation, determines the process gain of the system. Regulationswithin the United States mandate a minimum process gain of 10 dB, whichis determined from ten times the logarithm of the spreading ratio.Process gain is a measure of the ability of a spread spectrum system toresist interference. The larger the spreading ratio, the more resistantthe system is to interference within the receiver bandwidth. Widebandwidth modulation is reasonably resistant to low or moderate levelsof interference, but even systems with relatively high process gainsexperience difficulties when subject to strong interference.

[0011] When system throughout requirements dictate high data rates, theminimum process gain requirements in the regulations necessitate usingwide bandwidth transmissions. For example, a well-known system NCRWavelan uses Quadrature PSK modulation at 1 million symbols per secondto achieve 2 megabits per second (MBPS) data rates with a sourceinformation bandwidth available in the US ISM band at 902 MHz band. Inpractice, implementation constraints dictate that this system uses thefull 26 MHz band. Systems operating at other data rates, including theoriginal Norand system, utilize the full bandwidth at lower source datarates, e.g., 200 kilobits per second (KBPS). Utilization of a widerspreading bandwidth in this case provides greater rejection of multipathfading typical of the indoor RF signal propagation environment.

[0012] When it is anticipated the direct sequence systems may be used inenvironments with strong in-band interference, a design choice is toemploy channelization to reject interference. In the case of channelizeddirect sequence (DS) modulation, the spreading bandwidth is reduced to afraction of the total available bandwidth, and a frequency-agilefrequency generation systems is employed. By selecting the carrierfrequency of operation, communications can be established in a portionof the band where interference is not present. This technique requiresthe use of selective filters in the receiver intermediate frequency (IF)section to provide the necessary interference rejection. Thesechannelized DS systems utilize interference avoidance rather thanrelying on process gain to reject interference.

[0013] Utilization of frequency hopping spread spectrum systems isappropriate in environments where interference within the band ofoperation is not confined to particular portions of the band, but mayperiodically arise in various parts of the entire band. Frequentlyhopping is also useful as a multiple access technique. Use of multiplehopping sequences concurrently within a given location allows manysimultaneous communication sessions to be supported. Occasionally,devices operating on different hopping sequences will simultaneouslyoccupy the same channel within the band for short periods of time. Formoderate numbers of simultaneous hopping sequences, this occursinfrequently.

[0014] Frequency hopping also provides similar multipath rejectioncapabilities to wideband direct sequence modulation. If a particularchannel of operation is in a fade temporarily preventing communication,a jump to a frequency sufficiently removed from the faded frequency willoften allow communications to resume.

[0015] Frequency hopping systems require more protocol overhead to aidin establishing and maintaining synchronization between units sharing agiven hopping sequence. Additionally, the initial acquisition of thehopping sequence may require that an unsynchronized device scan the bandfor a period equivalent to may hop times. The overhead for directsequence systems is lower, with several bit-times usually allocated toreceiver acquisition at the beginning of each transmission.

[0016] Spread spectrum communications may not be appropriate for someapplications. For example, short hop communications such ascommunications between a portable hand-held terminal and a peripheraldevice such as a scanner or printer over a short distance is a very costsensitive application. Spread spectrum operation requires more circuitcomplexity and power consumption than is tolerable for this application.Simpler FM or AM techniques such as ON-OFF-Keying (OOK) may bedesirable.

[0017] Conventionally, the particular spread spectrum modulationtechnique is chosen according to the particular applications in whichthe data transceiver is to be utilized. For example, in a smallwarehouse having few RF barriers, minimal interference from cellular andwireless phones, and minimal amounts of communication traffic, radiotransceivers used therein might only employ direct sequence spreadspectrum transmission techniques. Thus, conventionally, suchtransceivers would be specifically designed, constructed and installed.However, after installation, if communication traffic or local noiseincreases, the communication might fail to function as required.Likewise, after installation, if RF barriers are installed or if thenetwork is moved to an urban environment with a great deal of noise fromneighboring installations, cellular and mobile phones, etc., the networkmay fail to meet the needs of the customer.

[0018] Similarly, a design might be based on a customer's needs for asmall store in a downtown urban area. Because of the greater likelihoodof a great amount of radio frequency traffic in the vicinity, thecustomer requires a radio which is free from interference from nearbyradio transmissions with little concern for operating range.Consequently, a different specific type of radio would be designed tomeet the needs of the corporation based upon the operating conditions inwhich the radio is to be used, for example using frequency hoppingmodulation.

[0019] In the exemplary installations mentioned above, each of theradios would be optimized to meet the needs of the customer. However, acustomer's needs continually change, and, if the particular applicationor environment were to change justifying a different spread spectrummodulation technique, the customer is either forced to change all oftheir radio transceivers or live with the under-performance theycurrently receive.

[0020] Moreover, in a typical network installation, a client may havediverse operational requirements. For example, the particularapplications of the radio unit may change several times within the sameday. The site may also have areas which are relatively noise and barrierfree and those which encounter heavy noise and barriers. Some areas mayhave high traffic volume, while others experience only occasionaltraffic. In such networks, a single radio transceiver design can neverprovide optimal performance in all areas. Sacrifices are made in thedesign characteristics of the transceiver in an attempt to provide bestperformance overall.

[0021] Similarly, in mobile contexts, a worker may require mobilecommunications to a vehicle based information system or forwarding to acentral communication facility through a vehicle based radio WANtransceiver. The characteristics of the communications medium for thisclass of operation vary greatly. Interference will vary from location tolocation. Additionally, it is necessary to allow operation if the workermoves away from the vehicle or inside a building structure. Because eachwireless local area network may have been designed for a particular setof criteria with particular spread spectrum operational abilities,mobile units may be non-functional within particular wireless local areanetworks.

[0022] Thus, there is a need in the art for a communication network thatoperates dynamically to optimize communication utilizing various spreadspectrum transmission techniques, considering the characteristics of RFnoise, neighboring interference, RF barriers, participating transceiverunit capabilities and applications to be performed in such dynamicoptimization.

[0023] It is another object of the present invention to provide a spreadspectrum RF transceiver module, for use in wireless network devices,which utilizes multiple spread spectrum modulation techniques providingmultiple configurable modes of data transmission, whereby modes may beselected to attain optimal transmission performance.

[0024] A further object of the present invention is to provide an RFdata transceiver module which combines frequency hopping and directsequence transmission techniques within a single design.

[0025] It is an object of the present invention to provide a spreadspectrum RF transceiver module which utilizes common media accessprotocols and interfaces for multiple nominal carrier frequencies andmodulation parameters.

[0026] It is a further object of the present invention to provide aspread spectrum RF transceiver utilizing 900 MHz transmission and havinga standard interface with common 2.4 GHz transmission.

[0027] It is a further object of the invention to provide a spreadspectrum RF transceiver which may be utilized in several different typesof multi-layered data communications networks.

[0028] Another object of the present invention is to produce a wirelesslocal area network and packet wireless data communication system that isflexible to operate reliably in varied and unpredictable RF propagationand interference environments.

[0029] A further object of the present invention is to provide awireless RF transceiver module capable of utilizing a variety ofoperational modes thereby allowing large business operation to purchasea single product meeting a multiple usage needs maximizing operationalflexibility and minimizing sparing and service concerns.

[0030] It is another object of the present invention to provide amodular wireless LAN modem capable of supporting multiple modes ofoperation under a single media access protocol with a standardizedinterface to a hand-held portable data terminal such that the wirelessLAN modem may dynamically change modes of operation transparently to thehost device, not requiring that the host device be aware of changes inthe modes of operation, or that operation of higher protocol layers beimpacted.

[0031] Yet another object of the present invention is to produce amodular wireless LAN modem that may be utilized for both in-premise andworker to vehicle application, and for short range communications toperipheral devices.

[0032] These and other objects of the invention will be apparent fromexamination of the drawings and remainder of the specification whichfollows.

SUMMARY OF THE INVENTION

[0033] The system and radio of the present invention to overcome thelimitations of the prior devices as well as other limitations thereforemay operate in any of a plurality of spread spectrum modes. A selectedspread spectrum mode, or set of spread spectrum modes, is based uponsystem characteristics as well as transmission characteristics within anoperating environment.

[0034] One particular operating environment relates to multi-hopwireless networks that are subject to in-band interference andmulti-path fading. However, in these systems, members (hereinafter“transceiver devices”) of the network may have different operatingcapabilities. Therefore, the system and radio of the present inventionprovide a mechanism for selecting spread spectrum modes of operation tosatisfy network member limitations, data transmission throughputrequirements, neighboring system non-interference requirements, as wellas noise tolerance requirements.

[0035] By providing a dynamic mechanism for selecting spread spectrummodes of operation, the present invention provides many import objectsand advantages that will become apparent with reference to the entirespecification and drawings. In particular, in one embodiment, acommunication network for collecting and communicating data isdisclosed. The network comprises a wireless access device and at leastone mobile terminal. The wireless access device comprises a controlcircuit and a first RF transceiver that selectively operates in one of aplurality of spread spectrum modes. The at least one mobile terminalcomprises a second RF transceiver that operates in at least one of aplurality of spread spectrum modes. The control circuit responds totransmissions received from the first RF transceiver to evaluatecommunication performance and dynamically selects one of the pluralityof spread spectrum modes of the first RF transceiver. Such selectionalso takes into consideration the at least one of the plurality ofspread spectrum modes of the second RF transceiver.

[0036] Further, the plurality of spread spectrum modes of the first RFtransceiver may comprise direct sequence transmission, frequencyhopping, channelized direct sequence and/or hybrid frequency hopping(direct sequence) modes. The control circuitry may evaluatecommunication performance through reference to received signal strengthindications, transmission success rate and neighboring cell operatingcharacteristics.

[0037] Other aspects may be found in a communication system forcollecting and communicating data using wireless data signaltransmission. Therein a wireless access device capable of communicatingwith a plurality of radios comprises a radio capable of operating in aplurality of spread spectrum modes. The wireless access device alsocomprises a spread spectrum mode controller responsive to transmissionsand data received for evaluating the data communication system and forcontrolling the radio to selectively operate in a spread spectrum modeamong a plurality of spread spectrum modes.

[0038] The wireless access device may further comprise circuitry forevaluating the plurality of spread spectrum modes to select a spreadspectrum mode of operation. Such selection may take involve theidentification of a common spread spectrum mode.

[0039] Yet other aspects can be found in a data communication systemhaving spread spectrum capability for collecting and communicating datausing wireless data signal transmission. Therein, an RF transceivercomprises an modulator having a spreader, a demodulator having adespreader, a controllable oscillator attached to the modulator anddemodulator, and control circuitry that both selectively enables thespreader and despreader and selectively controls the controllableoscillator to cause operation in one of a plurality of modes of spreadspectrum operation.

[0040] The data communication system may further comprising a hostcontroller that directs the control circuitry in the selection of theone of the plurality of modes of spread spectrum operation. The hostcontroller may comprise wireless access device control circuitry. Inaddition, the control circuitry may wirelessly receive instructionregarding selection of the one of the plurality of modes of spreadspectrum operation. Many other aspects of the present invention will beappreciated with full reference to the specification, drawings andclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

[0041]FIG. 1A is a perspective view of a wireless communication networkbuilt in accordance with the present invention which incorporatesdynamically adapting spread spectrum transceivers and supportingcommunication protocols;

[0042]FIG. 1B is a flow diagram illustrating the operation of a wirelessaccess device in accordance with present invention whereby multiplewireless devices having potentially different transceiver capabilitiesare supported;

[0043]FIG. 1C is a block diagram illustrating a radio transceiver builtin accordance with the present invention to provide multiple modes ofoperation;

[0044]FIG. 1D is a block diagram illustrating the operation of thewireless access device having the multi-mode transceiver of FIG. 1Cinstalled therein.

[0045]FIG. 2A is a front elevation view of one embodiment of a hand-heldportable data terminal having a transceiver module built in accordancewith the present invention;

[0046]FIG. 2B is a side elevation view of the hand-held portable dataterminal of FIG. 2A showing a module of the present invention;

[0047]FIG. 3 is a side evaluation view of the hand-held portable dataterminal of FIG. 2A showing a module of the present invention;

[0048]FIG. 4 is a side elevation view of the hand-held portable dataterminal of FIG. 2A showing a removably insertible module of the presentinvention;

[0049]FIGS. 4A, 4B and 4C illustrate in detail the cooperation between aradio module and the hand-held portable data terminal shown in FIG. 3.

[0050]FIG. 5 is a perspective view of another hand-held portable dataterminal which may incorporate the present invention;

[0051]FIG. 6 is a side elevation view of the data terminal of FIG. 5showing an extendibly retractable rotating carriage housing forreceiving a module incorporating the present invention;

[0052]FIG. 7 is an exploded view of a radio module incorporating thepresent invention;

[0053]FIG. 8 is an exploded view of a radio module of the presentinvention further containing a scanner;

[0054]FIG. 9 is an exploded view of a radio module of the presentinvention contained within a PCMCIA type housing;

[0055]FIG. 10 is a functional block diagram of the architecture of theradio modules of the present invention;

[0056]FIG. 1I is a conceptual block diagram of the operation of thetransmitter of FIG. 10 when operating in a direct sequence spreadspectrum transmission mode;

[0057]FIG. 12 shows a conceptual diagram of the operation of thereceiver utilized in conjunction with the transmitter of FIG. 1;

[0058]FIG. 13 is a block diagram of an embodiment of a receiver of thepresent invention;

[0059]FIG. 14A is a diagram of the pseudo-random number generator shownin FIG. 10;

[0060]FIG. 14B is a schematic block diagram illustrating the interactionof the pseudo-random number generator of FIG. 14A with traversefiltering and formatter circuitry of FIG. 10;

[0061]FIG. 15 is a block diagram illustrating the frequency generatorcircuitry as shown in FIG. 10;

[0062]FIG. 16 is a block diagram illustrating the transmitter circuitryas shown in FIG. 10;

[0063]FIG. 17 illustrates the circuitry for selecting between the modesof modulation of the present invention.

[0064]FIG. 18 is a block diagram of the MAC circuitry as shown in FIG.10;

[0065]FIG. 19 is a block diagram illustrating the host interfacecircuitry as shown in FIG. 10 for the radio module of FIG. 7 and for theradio/scanner module of FIG. 8; and

[0066]FIG. 20 is a block diagram illustrating the host interfacecircuitry as shown in FIG. 10 for the radio module of FIG. 9.

[0067]FIG. 21 is a diagram illustrating an alternate configuration ofportable data terminals according to the present invention.

[0068]FIG. 22A illustrates one embodiment of the data collectionterminal of the present invention, having both wired and wirelesscommunication capability.

[0069]FIG. 22B is a diagram illustrating a specific implementation ofthe portable terminal of FIG. 22A a single PCMCIA card contains not onlya multi-mode wireless transceiver, but also a wired modem transceiver.

[0070]FIG. 23 is a diagram illustrating the use of portable terminalsaccording to the present invention utilizing both wired and wirelesscommunication in a network configuration.

[0071]FIG. 24 is a diagram illustrating the use of portable dataterminals according to the present invention utilizing both wired andwireless communication to access separate subnetworks in an overallcommunication network.

[0072]FIG. 25a is a block diagram illustrating an embodiment of thepresent invention wherein a wireless access device uses a dedicatedcontrol/busy channel to manage a plurality of modes of communicationwith roaming terminals.

[0073]FIG. 25b is a drawing illustrating adcantageous operation of thewireless access device of FIG. 25a when two roaming terminals encounterhidden terminal conditions.

[0074]FIG. 25c is a flow diagram illustrating the functionality of thewireless access device of FIGS. 25a-b in managing communication using acontrol/busy channel.

[0075]FIG. 26a is a block diagram illustrating an alternate embodimentof that shown in FIG. 25a wherein a wireless access device uses aseparate transmitter for the dedicated control/busy channel and aroaming terminal uses either a shared multimode transmitter or amultimode transmitter and a separate busy/control channel receiver.

[0076]FIG. 26b is a drawing illustrating advantageous operation of thewireless access device of FIG. 26a when the two roaming terminalsencounter hidden terminal conditions.

[0077]FIG. 26c is a flow diagram illustrating the functionality of thewireless access device of FIGS. 26a-b in managing communication using acontrol/busy channel.

[0078]FIG. 27 is a block diagram illustrating a further embodiment ofthe present invention wherein channel selection and operating parametersare delivered by a wireless access device on a dedicated busy/controlchannel with or without multimode transceiver capabilities.

DETAILED DESCRIPTION OF THE INVENTION

[0079]FIG. 1A illustrates a communication network 1 incorporating theteachings of the present invention. The system comprises wireless accessdevices 2A, 2B and 2C, portable transceiver units 4A, 4B and 4C, awireless code reader 5 and a peripheral device 6. The wireless accessdevices 2A and 2B communicate directly on a wired network 3 to eachother and to other wired network devices (not shown). The wirelessaccess device 2C communicates with the wired network 3 and the wirelessaccess device 2A via wireless transmissions through the wireless accessdevice 2B.

[0080] The wireless access 2A-C may comprise wireless access points orwireless access servers to provide an interface among the portabletransceiver units 4A-C, the code reader 5, the peripheral device 6 anddevices on the wired network. Each of these wireless access devices 2A-Chas associated with it a range or cell of communication. For example,the portable transceiver units 4A-C may wander in and out of range ofthe wireless access device 2A. Similarly, they may wander in and out ofrange of the wireless access devices 2B-C, i.e., they may wander fromcell to cell. Each access device 2A-C, and many more as may provenecessary, are located to provide coverage of a customer's premises.Cell areas typically overlap somewhat to support ubiquitous coverage.

[0081] Because cells typically overlap slightly with one another, at anytime, a hand-held radio unit may communicate with at least two wirelessaccess devices. To avoid conflicts with transmissions in such overlapareas, it is desirable to configure neighboring cells operate withdifferent spreading codes, different hopping sequences or differentmodes, for example. However, when the portable transceiver unit 4B forexample passes from one cell to another, it cannot communicate with aneighboring wireless access device without changing its operatingcharacteristics. Thus, the present invention provides several techniquesfor accommodating devices wishing to communicate in a new cell.

[0082] Moreover, the wireless access devices 2A-C, peripheral device 6and code reader 5 may be capable of only some modes of wirelessoperation. Thus, the present invention provides a mechanism for each ofthe wireless access devices 2A-C to dynamically attempt to select acommon mode of appropriation for each participating device within itscell. Moreover, if a given mode of operation proves dissatisfactory, awireless access device may dynamically switch modes to attempt toachieve superior performance.

[0083] In particular, data throughput concerns and requirements, ambientnoise, power consumption of portable units, previously recorded successrates, received signal strength indications, neighboring cell operatingmodes and success rates, and mode capabilities of participating devicesare all considered in determining the mode in which to operate. Eachwireless access device engages in such consideration when initiallyestablishing communication in its cell, when attaching or detaching aparticipating device and as channel conditions are evaluated. In otherembodiments, less than all of such considerations need be made. Forexample, where all transceivers are known to operate in all availablemodes, consideration of this factor is not necessary. Similarly, if onlyone cell exists or if problems in overlap regions prove minimal,consideration of neighboring cell operation need not be engaged.Likewise, received signal strength alone may be used as a modeperformance indication.

[0084] Using lower power transmissions, a benefit to battery poweredportable transceiver units, requires the use of more wireless accessdevices to cover a premises. Lower power transmissions might also oralternately require a mode having a wider spreading bandwidth or slowerdata transfer rate to overcome the lower received signal strength. Inother cells that have minimal battery power concerns and little or nonoise, a spread spectrum mode may be chosen that provides higher datatransmission rates. In yet other cells experiencing significantbackground noise, a direct sequence spreading mode may be employed thatprovides greater noise tolerance.

[0085] In addition to changing modes, the wireless access devices 2A-Calso support changes to various mode parameters such as data segmentsizes, chipping rates, spreading code lengths, etc. By supportingdynamic changes in operating modes and mode parameters, thecommunication network 1 attempts to accommodate any transceiving devicethat enters any cell. This flexibility allows for expansion withoutreplacing existing equipment. An older radio transceiver may be able toparticipate with newer transceivers that may support newer modes ofoperation. The network 1 would attempt to accommodate such communicationin a common, older mode of operation.

[0086] RF signals are inherently subject to what is termed “multipathfading”. A signal received by a receiver is a composite of all signalsthat have reached that receiver by taking all available paths from thetransmitter. The received signal is therefore often referred to as a“composite signal” which has a power envelope equal to the vector sum ofthe individual components of the multipath signals received. If thesignals making up the composite signal are of amplitudes that add “outof phase” the desired data signal decreases in amplitude. If the signalamplitudes are approximately equal, an effective null (no detectablesignal at the receiver) results. This condition is termed “fading”.

[0087] Normally changes in the propagation environment occur relativelyslowly, i.e., over periods of time ranging from several tenths({fraction (1/10)}'s) of seconds to several seconds. However, in amobile RF environment, receivers (or the corresponding transmitters)often travel over some distance in the course of receiving a message.Because the signal energy at each receiver is determined by the pathsthat the signal components take to reach that receiver, the relativemotion between the receiver and the transmitter causes the receiver toexperience rapid fluctuations in signal energy. Such rapid fluctuationscan result in the loss of data if the amplitude of the received signalfalls below the sensitivity of the receiver.

[0088] Over small distances, the signal components that determine thecomposite signal are well correlated, i.e., there is a small probabilitythat a significant change in the signal power envelope will occur overthe distance. If a transmission of a data packet can be initiated andcompleted before the relative movement between the receiver andtransmitter exceeds the “small distance” data loss to fading is unlikelyto occur. The maximum “small distance” wherein a high degree ofcorrelation exists is referred to hereafter as the “correlationdistance”.

[0089] As expressed in wavelengths of the carrier frequency, thecorrelation distance is on half (½) of the wavelength, while a moreconservative value is one quarter (¼) of the wavelength. Taking thiscorrelation distance into consideration, the size of the data packet forsegmentation purposes can be calculated. For example, at 915 MHz (apreferred RF transmission frequency), a quarter wavelength is about 8.2centimeters. A mobile radio moving a ten (10) miles per hour, or 447centimeters per second, travels the quarter wavelength in about 18.3milliseconds. In such an environment, as long as the segment packet sizeremains well under 18.3 milliseconds, significant signal fluctuationsduring the duration of a packet transmission is unlikely. In such anpreferred embodiment, five (5) millisecond data packet segments arechosen which provides a quasi-static multipath communicationenvironment.

[0090] The faster the relative movement between a transmitter and areceiver the greater the effect of fading. Similarly, if the relativemovement is slower, fading is less pronounced. In many communicationenvironments, the degree of fading effects varies dramatically both fromtime to time and from installation to installation.

[0091] One example of a receiver making such a measurement of fading canbe found in the abandoned patent application of Ronald L. Mahany, U.S.Ser. No. 07/485,313, filed Feb. 26, 1990, which is incorporated hereinby reference. Specifically, in that reference, a received signalstrength indicator (RSSI) circuit is found in the receiver. The RSSIcircuit sample the signal strength of a transmission. If the signalstrength samples are evaluated in sequence and the trend analyzed, thedegree of fading can be measured. If the signal strength samplesdecrease in value, it is likely that fading is present in the network.

[0092] A transceiver using direct-sequence spread spectrum transmissionuses a spreading-code of a higher frequency than that of the data rateto encode the data to be sent. This higher frequency is achieved byincreasing the chip clock rate (wherein each chip constitutes an elementof the spreading-code). Using the same spreading code, the receiverdecodes the received signal while ignoring minor faults which occurredin transmission, providing noise immunity and multi-path signalrejection. The frequency and length of the spreading-code can be variedto offer more or less multi-path signal rejection or noise immunity.Although it may result in improved communication, increasing thefrequency or length of the spreading-code requires additional overheadwhich may not be justifiable unless necessary.

[0093] Frequency-hopping is the switching of transmission frequenciesaccording to a sequence that is fixed or pseudo-random and that isavailable to both the transmitter and receiver. Adaptation to thecommunication environment via an exchange in frequency-hopping operatingparameters is possible, for example, via selective control of thehopping rate or through the use of coding or interleaving. The greaterthe degree of frequency selectivity of the fading envelope (i.e., whenfading is significant only over a portion of the spectrum of hoppingfrequencies), the greater the benefit of such adaptation.

[0094] Particularly, a parameter indicating the hopping rate can bevaried to minimize the probability that the channel characteristics willdetrimentally change during the course of a communication exchange. Tovary the hopping rate is to vary the length of a hopping frame. Althoughmultiple data (or message) exchanges per hopping frame is contemplated,the preferred hopping frame consists of a single exchange of data, Forexample, in a polling environment, the hopping frame might consistof: 1) a base station transmitting a polling packet to a roamingterminal; 2) the roaming terminal transmitting data in response; and 3)the base station responding in turn by transmitting an acknowledgepacket. Each hopping frame exchange occurs at a differentpseudo-randomly chosen frequency.

[0095] For optimization, the hop frame length is adjusted to be as longas possible, while remaining shorter than the coherence time of thechannel by some safety margin. Although such adjustment does noteliminate the effects of fading, it increases the probability that thecharacteristics of the channel will remain consistent during eachhopping frame. Thus, in the preferred embodiment, if the polling packettransmission is successfully received, the probability of successfulreceipt of the data (or message) and acknowledge is high.

[0096] Another parameter for changing frequency-hopping performance isthat of coding. Coding on the channel for error correction purposes canbe selectively used whenever the probability of data or message loss dueto fading is high. In particular, coding methods which provide bursterror correction, e.g., Reed-Solomon coding, can be applied if the hoplength is likely to exceed the coherence time of the channel. Suchcoding methods allow some portion of the data to be lost andreconstructed at the expense of a 30-50% reduction in throughput. Theoperating parameter for coding indicates whether coding should be usedand, if so, the type of coding to be used.

[0097] An operating parameter indicating whether interleaving should beused also help to optimize the communication channel. Interleavinginvolves breaking down the data into segments which are redundantlytransmitted in different hopping frames. For example in a three segmentexchange, the first and second segments are sequentially combined andsent during a first hopping frame. In a subsequent hopping frame, thesecond and third segments are sequentially combined and transmitted in athird hopping frame. The receiving transceiver compares each segmentreceived with the redundantly received segment to verify that thetransmission was successful. If errors are detected, furthertransmissions must be made until verification is achieved. Onceachieved, the transceiver reconstructs the data from the segments.

[0098] Other methods of interleaving are also contemplated. For example,a simpler form of interleaving would be to sequentially send the datatwice without segmentation on two different frequencies (i.e., on twosuccessive hops).

[0099] As can be appreciated, interleaving provides for a redundancycheck but at the expense of data or message throughput. The interleavingparameter determines whether interleaving is to be used and, if so, thespecific method of interleaving.

[0100] In addition, any combination of the above frequency-hoppingparameters might interact to define an overall operating configuration,different from what might be expected from the sum of the individualoperating parameters. For example, selecting interleaving and coding,through their respective parameters, might result in a more complexcombination scheme which combines segmentation and error correction insome alternate fashion.

[0101] In the United States, data communication equipment operating inthe ultra-high frequency (UHF) range under conditions of frequencymodulation (FM) is subject to the following limitations.

[0102] 1) The occupied band width is sixteen kilohertz maximum with fivekilohertz maximum frequency deviation.

[0103] 2) The channel spacing is 25 kilohertz. This requires the use ofhighly selected filtering in the receiver to reduce the potential forinterference from nearby radio equipment operating on adjacent channels.

[0104] 3) The maximum output power is generally in the range of ten tothree hundred watts. For localized operation is a fixed location,however, transmitter power output may be limited to two watts, maximum,and limitations may be placed on antenna height as well. Theserestrictions are intended to limit system range so as to allow efficientreuse of frequencies.

[0105] For non-return to zero (NRZ) data modulation, the highestmodulating frequency is equal to one half the data rate in a baud.Maximum deviation of five kilohertz may be utilized for a highestmodulation frequency which is less than three kilohertz, but lowerdeviations are generally required for higher modulation frequencies.Thus, at a rate of ten thousand baud, and an occupied bandwidth ofsixteen kilohertz, the peak FM deviation which can be utilized for NRZdata may be three kilohertz or less.

[0106] Considerations of cost versus performance tradeoffs are the majorreason for the selection of the frequency modulation approach used inthe system. The approach utilizes shaped non-return-to-zero (NRZ) datafor bandwidth efficiency and non-coherent demodulation using alimited-discriminator detector for reasonable performance at weak RFsignal levels. However, the channel bandwidth constraints limit themaximum data “high” data rate that can be utilized for transmitting NRZcoded data. Significant improvements in system throughput potential canbe realized within the allotted bandwidth by extending the concept ofadaptively selecting data rate to include switching between sourceencoding methods. The preferred approach is to continue to use NRZcoding for the lower system data rate and substitute partial response(PR) encoding for the higher rate. The throughput improvements of NRZ/PRscheme over an HRZ/NRZ implementation are obtained at the expense ofadditional complexity in the baseband processing circuitry. An exampleof a transceiver using such an approach can be found in the previouslyincorporated patent application of Ronald L. Mahany, U.S. Ser. No.07/485,313, filed Feb. 26, 1990.

[0107] Partial response encoding methods are line coding techniqueswhich allow a potential doubling of the data rate over NRZ encodingusing the same baseband bandwidth. Examples of PR encoding methodsinclude duobinary and modified duobinary encoding. Bandwidth efficiencyis improved by converting binary data into three level, orpseudo-ternary signals. Because the receiver decision circuitry mustdistinguish between three instead of two levels, there is a signal tonoise (range) penalty for using PR encoding. In an adaptive baud rateswitching system, the effects of this degradation are eliminated byappropriate selection of the baud rate switching threshold.

[0108] Since PR encoding offers a doubling of the data rate of NRZencoded data in the same bandwidth, one possible implementation of aNRZ/PR baud rate switching system would be a 4800/9600 bit/sec system inwhich the low-pass filter bandwidth is not switched. This might bedesirable for example if complex low-pass filters constructed ofdiscrete components had to be used. Use of a single filter could reducecircuit costs and printed circuit board area requirements. This approachmight also be desirable if the channel bandwidth were reduced below whatis currently available.

[0109] The implementation with bandwidth available is to use PR encodingto increase the high data rate well beyond the 9600 bit/secimplementation previously described. An approach using 4800 bit/sec NRZencoded data for the low rate thereby providing high reliability andbackward compatibility with existing products, and 16K bit/sec PRencoded transmission for the high rate may be utilized. The PR encodingtechniques is a hybrid form similar to duobinary and several of itsvariants which has been devised to aid decoding, minimize the increasein hardware complexity, and provide similar performance characteristicsto that of the previously described 4800/9600 bit/sec implementation.While PR encoding could potentially provide a high data rate of up to20K bit/sec in the available channel bandwidth, 16K bit/sec ispreferable because of the practical constraints imposed by oscillatortemperature stability and the distortion characteristics of IF bandpassfilters.

[0110] All of the above referenced parameters must be maintained inlocal memory at both the transmitter and the receiver so that successfulcommunication can occur. To change the communication environment bychanging an operating parameter requires both synchronization betweenthe transceivers and a method for recovering in case synchronizationfails.

[0111] In one embodiment, if a transceiver receiving a transmission(hereinafter referred to as the “destination”) determines that anoperating parameter needs to be changed, it must transmit a request forchange to the transceiver sending the transmission (hereinafter the“source”). If received, the source may send an first acknowledge to thedestination based on the current operating parameter. Thereafter, thesource modifies its currently stored operating parameter, stores themodification, and awaits a transmission from the destination based onthe newly stored operating parameter. The source may also send a “noacknowledge” message, rejecting the requested modification.

[0112] If the first acknowledge message is received, the destinationmodifies its currently stored operating parameter, stores themodification, sends a verification message based on the newly storedoperating parameter, and awaits a second acknowledge message from thesource. If the destination does not receive the first acknowledge is notreceived, the destination modifies the currently stored parameter,stores the modification as the new operating parameter, and, based onthe new parameter, transmits a request for acknowledge. If the sourcehas already made the operating parameter modification (i.e., thedestination did not properly receive the first acknowledge message), thedestination receives the request based on the new parameters andresponse with a second acknowledge. After the second acknowledge isreceived, communication between the source and destination based on thenewly stored operating parameter begins.

[0113] If the destination does not receive either the first or thesecond acknowledge messages from the source after repeated requests, thedestination replaces the current operating parameter with a factorypreset system-default (which is also loaded upon power-up). Thereafter,using the system-default, the destination transmits repeated requestsfor acknowledge until receiving a response from the source. Thesystem-default parameters preferably define the most robustconfiguration for communication.

[0114] If after a time-out period the second request for acknowledgebased on the newly stored operating parameters is not received, thesource restores the previously modified operating parameters and listensfor a request for acknowledge. If after a further time-out period arequest for acknowledge is not received, the source replaces the currentoperating parameter with the factory preset system-default (which is thesame as that stored in the destination, and which is also loaded uponpower-up). Thereafter, using the common system-default, the sourcelistens for an acknowledge request from the destination. Once received,communication is reestablished.

[0115] Other synchronization and recovery methods are also contemplated.For example, instead of acknowledge requests originating solely from thedestination, the source might also participate in such requests.Similarly, although a polling protocol is used to carry out thecommunication exchanges described above, carrier-sense multiple-access(CSMA) or busy tone protocols might alternately be used.

[0116] In the embodiment illustrated in FIG. 1A, various modes ofoperation are dynamically controlled by the wireless access devices2A-C. Such control involves the consideration by each wireless accessdevice of many factors such as: 1) received signal strength; 2)success/fail rates; 3) mode capabilities of participating devices; 3)neighboring access device operation and performance; 4) applicationsupport required; and 5) power concerns. In addition to modifying theparameters of a particular mode (as previously mentioned), the wirelessaccess devices may also select from a plurality of modes (as describedin more detail below in reference to FIG. 10).

[0117]FIG. 1B is a flow diagram illustrating the operation of a wirelessaccess device in accordance with present invention whereby multiplewireless devices having potentially different transceiver capabilitiesare supported. In particular, a wireless access device manages ongoingcommunication within its cell with a previously selected mode and modeparameters at a block 401. At a block 403, the wireless access deviceidentifies an attach request from a wireless transceiver (hereinafterthe “requesting transceiver”) that may have wandered into the cell. Theaccess device 403 responds at a block 405 by identifying the availablemodes of operation of the requesting transceiver. At a block 407, themodes are added to a mode table, which stores the available modes of allthe participating devices. Note that a requesting transceiver onlycommunicates the availability of those modes which are both possible(determined by the transceiver's design) and useful (determined by acurrent application).

[0118] If the requesting device is capable of operating in the currentlyselected mode, as determined at a block 409, the wireless access devicecommunicates mode information and parameters to the requestingtransceiver at a block 413. Thereafter, the wireless access devicereturns to the block 401 and services all participating devicesincluding the requesting device in the current mode with currentparameters.

[0119] Alternatively, if the requesting device has a limited number ofoperating modes, at the block 409 the current mode may not be apossibility. If the requesting device is not capable of operating in thecurrent mode, the wireless access device attempts to select a new modeat a block 411. If at least one common mode can be found, e.g., if allthe participating devices and the requesting device have at least onecommon mode, the wireless access device chooses the common mode that itbelieves will offer optimal performance. Thereafter, at a block 413, thewireless access device communicates the selected mode and parameterinformation to the requesting transceiver at the block 413 and returnsto the block 401. At the block 401, because a new mode has beenselected, the wireless access device vectors to service the event at ablock 419. At a block 421, the wireless access device broadcasts themode and parameter information, and, at a block 423, changes its ownmode. Thereafter, the wireless access device returns to service ongoingcommunication in that mode at the block 401.

[0120] If however a common mode cannot be found for a requestingtransceiver at the block 411, the requesting transceiver is rejectedfrom participating. In such a case, the customer must identify theradios causing the limitations and upgrade them. In another embodiment,the wireless access device operates in a time shared configurations,switching between two or more modes in a sequential fashion. In thisembodiment, however, the overall delays in the system may still justifyupgrading the radio transceiver(s) causing the limitations.

[0121] During the course of ongoing operation at the block 401, thewireless access device monitors channel performance (a variety offactors described in more detail above), and compares such performanceto available other common modes of operation and considers potentialparameter modifications. In particular, as represented by the block 429,if channel conditions degrade below a predefined threshold, the wirelessaccess device vectors to consider changing modes. At a block 431, thewireless access device consults the mode table. If a new mode isavailable and warranted, per a determination at a block 433, thewireless access device responds by selecting an alternate common mode atthe block 435, resets the conditions that caused the vectoring andreturns to the block 401 to complete the mode change via the blocks 419,421 and 423. Similarly, each time a participating transceiver detachesfrom the cell (through either active detachment or aging) as representedby an event block 445, the wireless access device removes thattransceiving device's mode information from active status in the modetable and attempts to choose a better common mode via the blocks 431,433, 435 and 437. Although not shown, the wireless access device mightalso periodically attempt to choose a better common mode, withoutrequiring channel conditions to change or degrade or participants todetach.

[0122]FIG. 1C is a block diagram illustrating a radio transceiver usedin wireless access devices and any transceiving device, such as aprinter, code reader, hand-held terminal, etc., and built in accordancewith the present invention to support multiple modes of operation. Thetransceiver module 501 comprises control circuitry 503, a modulator 505,a demodulator 507, and oscillator 509 and a switch circuit 511. Thecontrol module may have either an internal or external antenna attachedthereto, i.e., an antenna 513.

[0123] The control circuitry 503 manages the operation of the othercomponents of the transceiver module 501. The control circuitry 503receives instructions and data to be transmitted from a host unit (notshown) via a wired communication link 515. The control circuitry 503deliver such data to the modulator 505 for modulation (and possiblyspreading). Thereafter, the data is delivered to the antenna 513 via theswitch 511. Data and control signals received by the antenna 513 passesthrough the switch 511 to the demodulator 507 for demodulation (andpossibly despreading). The control circuitry 503 receives thedemodulated data or control signals for processing and/or delivery tothe host unit through the link 515.

[0124] The control circuitry 503 causes the selection of operatingparameters and modes as described previously and in reference to FIG.1B. Specifically, the control circuitry 503 sets the configuration ofthe modulator 505, demodulator 507 and oscillator 509. For example, tooperate in a direct sequence spread spectrum mode, the control circuitry503: 1) sets the base frequency of the oscillator 509; 2) sets relatedmode parameters such as the chipping rate; and 3) delivers enablesignals and a spreading code to a spreader circuit 515 and despreadercircuit 517 of the modulator 505 and demodulator 507, respectively. Tooperate in a frequency hopping mode, the control circuitry 503: 1)establishes related parameter settings; 2) disables the spreading anddespreading circuits 515 and 517; 3) selects a hopping sequence offrequencies; and 4) directs the oscillator 509 through the sequence. Tooperate in a hybrid, direct sequence, frequency hopping mode, thecontrol circuitry 515: 1) establishes related parameter settings; 2)delivers enable signals and a spreading code to a spreader circuit 515and despreader circuit 517; 3) selects a hopping sequence offrequencies; and 4) directs the oscillator 509 through the sequence.Similarly, the control circuitry 503 may select any modes, e.g., themodes identified in reference to FIG. 10 below, and set all parametersrelated thereto.

[0125]FIG. 1D is a block diagram illustrating the operation of thewireless access device having the multi-mode transceiver of FIG. 1Cinstalled therein. In particular, a transceiver module 501 (as describedin relation to FIG. 1C) is installed within a wireless access device503. The wireless access device 503 contains control circuitry 505 andinterface circuitry 507 for communicating with a wired network 509. Inaddition to providing typical access device service, the controlcircuitry 505 of the wireless access device 503 manages all mode andparameter changes for the transceiver module 501. The control circuitry505 monitors, among other factors, the historical performancecharacteristics of each mode, neighboring access device modes,parameters and performance and current mode performance (via receivedsignal strength indications and success/failure rates). The controlcircuitry 505 also maintains and updates the mode table, attachment anddetachment of participants, as described above in reference to FIG. 1Bfor example. The control circuitry 505 performs such functionality viacontrol signals delivered to the control circuitry of the transceivermodule 503.

[0126] When installed in a portable/mobile or stationary transceiverunit (e.g., peripheral device, code reader, hand-held terminal, etc.), atransceiver module responds to communication control through commandsreceived from the wireless access device while attempting to attach.Such commands direct the mode and parameters of operation of thetransceiver module in the transceiver unit. In addition, the controlcircuitry of the transceiver module 501 directs entry of a default modeand default parameters prior to receiving direction from a wirelessaccess device. Although the transceiver module 501 may receiveadditional mode and parameter commands from the host controller withinthe transceiver unit, in need not do so. Such local control by atransceiver unit, however, may prove advantageous in other wirelessnetwork embodiments or in specific applications. For example, othernetwork embodiments might involve only two transceiver units without awireless access device. As such, the transceiver units may negotiate amode and related parameters amongst themselves, controlling such changesvia host processors within the transceiver units. Negotiation of modeand parameter changes might also involve channel condition monitoring orother factors currently assigned to the wireless access device.

[0127]FIG. 2A illustrates a hand-held portable data terminal whichincorporates the present invention, designated generally by the numeral10. The data terminal 10 may be one of several data terminals in a localarea network which utilizes radio frequency (RF) communications for datatransfer. The data terminal 10 illustrated is a mobile data unit thatincludes a radio transceiver unit incorporating the present invention.Of course, as has been previously described, the present invention maybe incorporated into stationary units as well as mobile units. Further,the stationary units may comprise wireless access points, other functionperforming devices such as printers, stationary scanners, or otherdevices. Moreover, mobile units incorporating the present invention neednot comprise the hand-held radio format illustrated in FIG. 2A. Themobile units could be installed in vehicles, worn by a user, orinstalled in any other fashion that causes the device to be mobile.

[0128] The data terminal 10 includes an antenna 12 is disposed at thetop end 14 of the data terminal for radio frequency transmission andreception. The data terminal may include a display screen 16 fordisplaying program information and for interfacing the operator with thedata terminal 10. The display screen 16 may be a reflective super-twistliquid crystal display (LCD), for example. The data terminal 10 mayinclude a keypad 18 having a plurality of keys for entering data intothe data terminal 10 and for control of the data terminal 10 by theoperator.

[0129]FIG. 2B shows the data terminal 10 of FIG. 2A which includes amodule in which circuitry for accomplishing the present invention isdisposed. The data terminal 10 has a modularly attached radio module 20which also contains scanning circuitry in addition to radio circuitry.The antenna 12 of FIG. 2A is affixed to the radio/scanner module 20 andmay be a type suitable for portable battery powered electronic devices.The radio/scanner module 20 has an extended outer shell 24 in order tocontain both the radio and the scanner circuitry. A button 26 may bedisposed on either or both sides of the radio/scanner module 20 toactivate the scanning circuitry and scan encoded data, such as thatcontained in a bar code or two dimensional image. The module 20 could,in another embodiment, include a digital camera or other functionalequipment. As illustrated, the radio/scanner module 20 is constructed tobe modularly received by a recession 28 in the data terminal such that acontinuous unit is formed by attaching the module 20 to the dataterminal.

[0130]FIG. 3 shows a side view of another embodiment of a data terminal10 with an alternate modular radio module attached thereto. The module30 includes a radio incorporating the teachings of the present inventionbut does not include the image capture electronics of the radio/scannermodule 20 of FIG. 2B. Because the module 30 is more compact than radioscanner module 20 of FIG. 2B, the body of radio module 30 is generallyflush with the body of the data terminal 10 when attached thereto.

[0131]FIG. 4 shows a data terminal 10 that is removably attachable tothe radio/scanner module 20 of FIG. 2B. The motion required forattachment of the module 20 to the data terminal 10 generally followsthe direction of line 32. The module 20 is positioned toward theterminal 10 and then locked into place by a downward movement. L-shapedlatches 34 may be used to removably secure the module 20 to the terminal10.

[0132]FIGS. 4A, 4B and 4C illustrate in detail the cooperation between aradio module and the hand-held portable data terminal shown in FIG. 3.The radio module 30 houses a radio unit 340. An antenna connector 342connects to antenna connector pins 344 at an end of the radio unit 340to provide electrical connection to an antenna which may be internallyor externally mounted on the module 30. An array of connecting pins 346preferably connect the radio unit 340 to the data terminal which mayhave a receptacle for receiving the connecting pins 346. The radiomodule 30 may include a hand strap 348, one end of which being connectedto the module 30 and the other end being connected to the terminal 10,to facilitate manipulation of the terminal 10 in one hand and to preventaccidental dropping, for example.

[0133]FIG. 5 depicts another type of hand-held portable data terminal 36that incorporates the present invention and that is designed to receivestandard PCMCIA computer feature card modules. The terminal 36 may havea module carriage housing 38 which may receive various types of PCMCIAcards 40: Type I (3.3 mm in thickness), Type II (5.0 mm in thickness) orType III (10.5 mm in thickness) PCMCIA sized modules for example.

[0134]FIG. 6 shows the data terminal of 36 of FIG. 5 having a rotatablyextendible and retractable carriage housing 38. The carriage housing 38is shown in the extended position holding a Type III PCMCIA module 42which may, for example, contain the radio circuitry of the presentinvention.

[0135]FIG. 7 is an exploded view of the internal components of a radiomodule 30 of the present invention such as the module 30 of FIG. 3. Thecircuitry of radio module 30 of the present invention such as the module30 is preferably mounted on a circuit card assembly (CCA) board 44containing, for example, the transmitter and receiver electroniccomponents (not shown). The radio CCA 44 may have metallic coverings, orcans (not shown), soldered to the board over critical radio componentsto provide two-way electromagnetic shielding to reduce or eliminateradio frequency interference.

[0136] In embodiment of FIG. 7, the radio module CCA 44 is containedwithin a metallic radio cover 46 to provide electromagnetic shielding ofthe radio CCA 44. The radio CCA 44 and radio cover 46 may be attached toa mounting frame 48 which provides supporting structure for the internalcomponents of the radio module 30. Radio cover 46 and mounting frame 48may be fabricated of ABS type plastic or of a conductive metal toprovide electromagnetic shielding. The radio CCA 44 and the radio cover36 may be attached to the mounting frame 48 by a plurality of fasteners50 which may be four #2 screws in a preferred embodiment.

[0137] An internal antenna 52 may be connected to the radio circuitry ofthe radio CCA 44 in lieu of the external linear antenna 12 shown in FIG.2A and completely contained within the radio module 30. The radio module30 may utilize the antenna means of U.S. Pat. No. 5, 322, 991 issuedJun. 21, 1994 and assigned to NORAND Corporation of Cedar Rapids, Iowa,the assignee of the present application, Said U.S. Pat. No. 5,322,991 ishereby incorporated by reference in its entirety. The antenna 53 maycomprise a quarter-wavelength single loop of wire of approximately 83 mmfor transmissions near 900 MHz. When the loop antenna 52 is driven bythe output of the radio module 44, a uniform circulatory current flowingthrough the antenna 52 results in a radiation pattern similar to that ofa magnetic dipole. The antenna 52 preferably has a nominal impedance of50 S.

[0138] An internal shield 56 may be utilized and inserted between theradio circuit card assembly (CCA) 44 and the radio interface card (RIC)58 which contains the electronic circuitry necessary6 to interface theelectronics of the radio CCA 44 with the electronics of the dataterminal 10 of FIG. 2A. The radio interface card 58 may be a type usedfor a 2.4 GHz radio since the interface to the radio CCA 44 is baseband.The 900 MHz radio 44 of the present invention may be designed to appearas a 2.4 GHz radio accepting the same frequency control inputs andemploying the same media access control protocols as a 2.4 GHz radio.

[0139] Electrical connectors 60 may be mounted at an end of the radiointerface card 58 for providing electrical connection to the CPU board(not shown) of the portable data terminal with which the radio module 30is utilized, such as terminal 10 of FIG. 2A. A mounting fastener 62,which may be a screw, fastens the radio interface card to the radiomodule assembly 30. An acoustic-electric transducer such as buzzer 64may be included with the radio module 30 and electronically connected tothe radio CCA 44 5to provide the operator with audio information andcues, for example a beep or buzz when the radio module 30 is powered on.Frame mounting screws 66 may be utilized to fasten the assembly to theouter shell 68 via mounting frame 48. The entire module assembly may bewrapped in a metallic foil to provide electromagnetic shielding to theradio module 30. The outer shell 68 is preferably a type of ABS plasticand is formed to modularly and contiguously fit the recession 28 of thedata terminal 10 as shown in FIG. 2B.

[0140]FIG. 8 is an exploded view of the radio/scanner module 20illustrated in FIGS. 2B and 4. The components and assembly thereof ofthe radio/scanner module 20 are substantially similar, with some slightmodifications thereof where necessary, to that of the radio module 30 ofFIG. 7, the principle difference being the addition of scanner circuitryin the radio/scanner module 20 for reading optically readable data filessuch as standard bar codes. The radio/scanner module 20 includes radiointerface card 58 with electrical connectors 60, mounting frame 48,internal shield 56, radio CCA 44, antenna 52, radio cover 46, and buzzer64 as shown in FIG. 7 (and as described in the discussion of FIG. 7).

[0141] In addition to the above components, the radio/scanner module 20includes a scanner printed circuit board 70 on which the scannerelectronic circuitry are mounted. A flex circuit connection assembly 72may be utilized to interconnect the electronic circuitry, such as thecircuitry of scanner card 70 and interface card 58. The outer shell 74of the radio scanner module is substantially similar to the outer shell68 of radio module 30 as shown in FIG. 7, modified to accommodate theadditional components of the radio/scanner module 20.

[0142] A rubber nose end cap 76 may be attached to the forward end ofthe outer shell 74 for providing impact shock absorption and protection.A seal label 78 may be used to provide an adhesive seal between rubbernose end cap 76 and outer shell 74. A lens 80 mounted with a lens sealsupport 82 may be disposed in the rubber end cap 76 to provide a sealedlight aperture for the scanner circuitry. Scanning of an opticallyreadable data file may be controlled with a scam button 86 which coversam input keyboard and elastomer 84 and is supported by a scan buttonbezel 88 mounted in a button aperture 90 on a side of the outer shell74. The radio/scanner may have a plurality of scan or input buttons 86.For example, an additional button may be provided on the side of theouter shell 74 opposite the button 86 shown in FIG. 8.

[0143] Frame mounting screws 92 are provided to mount the mounting frame48 containing the module assembly to the outer shell 74. The outer shell74 and radio/scanner module are formed to modularly and contiguouslyattach to the data terminal 10 as illustrated in FIGS. 2B and 4 in amanner substantially similar the attachment of radio module 30 to dataterminal 10. The entire module assembly 20 may be wrapped in a metallicfoil to provide electromagnetic shielding to the radio module 20.

[0144]FIG. 9 is an exploded view of the PCMCIA Type III radio module 42of FIG. 6. The PCMCIA radio module 42 may also be constructed within asmaller sized PCMCIA module such as Type II or Type I enclosure bycombining the circuitry of the radio interface card 58 and the radiocircuit card assembly 44 on a single printed circuit board, for example.The PCMCIA radio module 44 may contain the radio circuit card assembly44 and the radio interface card 58 of FIGS. 7 and 8. The radio interfacecard 58 is preferably adapted to conform to PCMCIA device interfacestandards for utilization in PCMCIA radio module 42. The circuitry ofthe radio CCA 44 and the radio interface card 68 may be interconnectedby a board to board connector 94. Alternatively, all of the circuitry ofthe RIC 58 and the CCA 44 may be combined on a single printed circuitboard for smaller sized radio modules (20, 30 or 42).

[0145] Standoffs 96 may be soldered directly to the radio interface card58 and are provided to separate the radio CCA 44 from the radiointerface card 58 and to provide attachment thereto with fasteners 98(preferably #2-56 screws). The screws 98 preferably attach the radio CCA44 to a custom PCMCIA Type III frame 100 which provides structuralsupport and protection of the circuit boards 44 and 58. A PCMCIAelectrical receptacle 102 may be provided to electrically connect theradio module to standard PCMCIA connectors in the electronic equipmentin which the module 42 is to be utilized, such as the data terminal 36of FIGS. 5 and 6.

[0146] An antenna connector 104 may be mounted on the radio CCA 44 forconnection of the module to an antenna which may be, for example, theantenna 12 of FIG. 2A, the antenna 52 of FIGS. 6 and 7 of the antennameans of U.S. Pat. No. 5,322,991 issued Jun. 21, 1994 incorporatedherein. Alternate antenna clips 106 may be utilized for adapting theradio module 42 to various antenna connection configurations.

[0147] The PCMCIA radio module 42 may be contained within top and bottomcovers 108 and 110 respectively which are preferably comprised of tinplated cold rolled steel. The module covers 108 and 110 may provide twoway electromagnetic shielding of the radio frequency circuitry. When theradio module 42 is assembled and contained within top cover 108 andbottom cover 110 the module preferably conforms to PCMCIA Type IIIdimensions. The module 42 may also be adapted to conform to PCMCIA TypeII or Type I dimensions as well.

[0148] The transceiver module as shown in FIG. 9 may be utilized in astandard desktop or portable computer such as a laptop computer which isdesigned to utilize standard PCMCIA computer modules. The portablecomputer may be implemented as part of a multilayered communicationnetwork such as a communications node to communicate, for example, withseveral data terminal in a connected wired network, as well as withnodes in the wireless network. In this fashion, the computer could serveas a wireless access point, a wireless access server, or another type ofwireless device providing access to the wireless network. A preferredembodiment of the present invention implements Layer 1 (the physicallayer) and the medium access control (MAC) sub-layer of Layer 2 (thedata link layer) of the International Standards Organization ReferenceModel (ISORM) operating under an ODI or NDIS driver. A driver interfaceto the MAC sub-layer allows the utilization of industry standardmulti-layer communications protocol above the MAC sub-layer.

[0149]FIG. 10 is a functional block diagram of an embodiment of theradio modules 20, 30 and 42 of the present invention. The components ofFIG. 10 implement the teachings of the present invention by causing theradio module to be operable in any of a plurality of spread spectrummodes depending upon system and transmission conditions. The componentsillustrated could be found in a mobile unit or a stationary unit toprovide equivalent functionality in the units. In one embodiment, atleast one stationary unit and a plurality of mobile units in a wirelesslocal area network are capable of operating in a plurality of spreadspectrum modes such as direct sequence, channelized direct sequence,frequency hopping, channelized frequency hopping, or hybrid modes. Thecomponents illustrated in FIG. 10 allow the radio modules to operate insuch a fashion.

[0150] The antenna section includes an antenna 112 for transmitting andreceiving radio frequency energy. The antenna 112 may be one of theantennas described in the discussion of FIGS. 7, 8 and 9. The radiocircuitry corresponds to the radio circuitry of the radio CCA 44 ofFIGS. 7, 8 and 9 and contains the receiver circuitry 114, thetransmitter circuitry 118 and the frequency generator (“FREQ.GENERATOR”) 116.

[0151] The radio frequency (RF) transceiver 298 of the present inventioncomprises a receiver 114 and a transmitter 118. The transmitter 118preferably comprises a data formatter and spreader (“BASE BANDFORMATTER/SPREADER”) 124, a selectable transversal filter 150 comprisingprogrammable transversal filters (“PROGRAMMABLE TRANSVERSAL FILTER”) 146and 148 (See FIG. 11), a binary phase shift keying (BPSK) modulator(“BPSK MODULATOR”) 130, and a transmitter up converter and lineartransmit power amplifier (“TX UP CONVERTER & AMP”) 314. The receiver 114preferably comprises a receiver down convertor 304, a selectablebandwidth intermediate frequency (IF) stage (“SELECTIBLE BW IF”) at afixed IF center frequency, a non coherent I/Q base band converter(“BASEBAND CONVERTOR”), and a demodulator/despreader (“DEMOD.DESPREAD.”).

[0152] A common radio frequency bandpass filter (“BPF”) 399 is shared byboth the transmitter 114 and the receiver 118. The transceiver 298 iscoupled to an antenna 112 through an antenna switch circuit 302. Afrequency generator 116 is common to both the receiver 114 and thetransmitter 118, producing a frequency agile main VCO output (“MAINVCO”) 332, and an auxiliary output (“AUX VCO”) 334 at twice the IFfrequency. A divide by 2 circuit (316 and 318) in the transmit path ofthe auxiliary VCO signal 334 is activated when the transceiver 298 isswitch to the transmit mode.

[0153] The transmit operation the media access control (MAC)microprocessor (“MAC μP”) 128 enables the various transmit circuitsthrough the control bus (see CONTROL of FIG. 18). In particular,however, the MAC μP 128 controls the various components illustrated inFIG. 10 as illustrated. However, in other embodiments of the presentinvention, the MAC μP 128 may control only a portion of the componentsor even more of the components. To implement the teachings of thepresent invention, the MAC μP 128 controls the various elementsillustrated in FIG. 10 so as to perform transmission and reception inany of the various spread spectrum modes. In order to accomplish suchvarious modes, the MAC μP 128 must control the frequency generator 116to cause modulation over all of a spreading bandwidth via variations inthe MAIN VCO frequency. In addition, the MAC μP 128 provides control tothe modulator 130, RECEIVER DOWN CONVERTER 304, TX UP CONVERTER & AMP314, the SELECTABLE BW IF 322, the MODULATOR 130, the SELECTABLETRANSVERSAL FILTER 150, the DEMODULATOR DESPREADER 184, and theFORMATTER/SPREADER 124 in order to cause the circuitry to perform in thevarious spread spectrum modes.

[0154] As is known, each of the various spread spectrum modes requirespackaging, modulating, transmitting, and receiving data in particularformats and frequencies. Thus, the MAC μP 128 provides control over theelements illustrated in FIG. 10 in a fashion so as to enable each of thevarious spread spectrum modes. Techniques known in the art may beemployed to cause the components illustrated in FIG. 10 to perform inparticular spread spectrum modes.

[0155] The functions of the baseband formatter/spreader 124 may becontained in a digital application-specific integrated circuit, or ASIC,(not shown) with circuitry configurable to the desired transmission modeby the control microprocessor 128. The ASIC preferably produces a clockat the correct data rate for the selected mode which is used to timeserial transfer of a data frame from the transmit data output of the MACμP 128 (see TXD of FIG. 18).

[0156] In the direct sequence (DS) modes, the data is mapped into I/Qsymbols for either BPSK or QPSK modulation. The ASIC generates asynchronous chip clock at a multiple of the symbol rate that is appliedto the pseudo-random number (PN) generator of FIG. 14A to produce achipping sequence at the selected spreading ratio. The exact chippingsequence is selected by programming the feedback select of FIG. 14A. Thechipping sequence is multiplied with the I/Q data symbols by use ofexclusive OR gates. The selected data rate and spreading ratio determinethe main lobe bandwidth of the transmitted signal. The bandwidth of themain lobe and side lobes are reduced by applying the transversal filters(146 and 148 of FIG. 148), which comprise circuitry of the transversalfilter 150 of FIG. 10 with the shift registers operating at the chippingrate rather than the symbol rate. The main lobe bandwidth is limited toapproximately 1.6 times the chip clock frequency.

[0157] The remainder of the Transmitter 118 is a standard I/Q modem. TheI/Q waveforms are applied to a quadrature PSK modulator operating at ½the Auxiliary VCO frequency. The modulated signal is filtered to reduceharmonic content, then undergoes a second conversion with the Main VCOoutput 332 to produce a final output frequency. This signal is filteredto reduce the image of the mix product from this second conversion, andthen amplified by the antenna 112 through the antenna switch 302 and RFbandpass filter 300.

[0158] In the receive mode, the receiver circuitry 118 is switched onand the transmitter circuitry switched off through the controlinterface. Incoming signals present at the antenna are amplified andconverted to the IF frequency by mixing with the main VCO output 332.The output of the receiver down converter 304 is applied to theselectable bandwidth IF filter 322, which is programmed to the correctbandwidth for the selected mode of operation by the MAC μP 128. Thefilters 174, 176 and 178 provide rejection of out of band signals forthe selected signal bandwidth.

[0159] The filtered output is applied to a limiting amplifier, then tothe I/Q baseband converter 312. The limiter 182 produces a receivedsignal strength indication that is proportional to log of the signalenergy in the IF. This is applied to an A/D converter 126 then to thecontrol μP 128. This function is useful for detecting proximity to thetransmitting unit, or to an interferor, and is also useful as an OOKdetector.

[0160] The baseband converter 312 contains an internal divide-by-twocircuit which produces a carrier at ½ the Auxiliary VCO frequency whichis also at the nominal IF frequency. This is mixed with the limited IFsignal to produce baseband I/Q waveforms. These in turn are applied tocomparators that serve as hard decision circuits, then to the correlator330 (see FIG. 17) within the ASIC.

[0161] The frequency generation system 116 must be programmed to producethe Main VCO output. A serial interface within the control bus providesthis capability. In the DS modes the Main VCO is programmed to thecorrect channel frequency and remains there until a mode change or theneed to avoid interference is detected. For wideband DS operation, TheMain VCO is programmed to the center of the frequency range.

[0162] For FH or hybrid operation, i.e., frequency hopping combined withdirect sequence operation, the Main VCO is periodically reprogrammed toprovide the hopping function. The MAC μP 128 maintains a timer, andtable of channels representing the hop sequence. When the timer expires,the MAC μP initiates the hop to the next frequency in the sequence.Frames passed between the various devices within the WLAN establishshared timing references so that all units hop in synchronism.

[0163] The MAC μP 128 provides mode control, host interface, transmitframe generation, channel access control, receive frame processing,retries of erred packets, power management of radio circuitry, andfrequency hopping control. The frequency hopping control is a supersetof the remaining functions, allowing common programming of the remainingfunctions for both DS and FH.

[0164] The host interface for the PCMCIA version is compliant with thePCMCIA physical interface. The software interface is structured tocomply with the factory industry standards NDIS and ODI formats.

[0165] Data to be transmitted is sent via a bus 131 to the MAC circuitry128 from a host unit. The data to be transmitted is be modulated by themodulator 130 and frequency controlled by the spreader 124 according tothe particular spread spectrum transmission mode to be utilized. Thespreader 124 receives a chipping clock input that is at a frequencymultiple of the source data frequency. The output of the spreader 124 issent to the transmitter up converter and amplifier 314 to transmit theRF data signal through the antenna 112.

[0166] The radio modules of the present invention may utilize severalmodes of spread spectrum RF data transmission. In one embodiment of thepresent invention, the various modes can be user selectable dependingupon the particular application in which the radio modules are to beutilized. In another embodiment, the modes of operation are beautomatically and dynamically selected, e.g., by the MAC μP 128 basedupon criteria previously described. Such selection might also beperformed by or with the assistance of the terminal unit or a digitalsignal processor provided for such task.

[0167] In a particular example, a microprocessor in the host terminalmay retrieve stored modes of operation utilized on the previous day towhich a higher logical multiplier is used to determine whichtransmission mode or modes are to be selected for that day's datatransmissions. Additionally, data such as the average signal strength,most frequently utilizes transmission mode, the average level ofinterference and noise for a particular mode or transmission successrate (e.g. percentages of transmissions) may be saved in nonvolatilememory and factored into the mode selection routine. A description ofparticular spread spectrum modes follows in Table 1. The modulationtechniques as described in Table 1 may be direct sequencing (DS),frequency hopping (FH) or on-off-keying (OOK) or a combination thereof.The rate at which data may be transmitted is given is kilobits persecond (kb/s) and the channel bandwidth is given for each mode for theoperational frequency range of 902 to 928 MHz. The full bandwidth of anembodiment of the radio is 26 MHz Table 1. TABLE 1 Spread SpectrumTransmission Modes MODULATION DATA MODE TECHNIQUE RATE BANDWIDTH 1 DS 250 kb/s full band 2 CHANNELIZED DS  250 kb/s  5 channel   5 MHz 3 DS 500 kb/s full band 4 FH  250 kb/s  50 channels  500 kHz 5 FH/DS   10kb/s  50 channels  500 kHz 6 OOK 19.2 kb/s  50 channels  500 kHz 7 DS  10 kb/s  50 channels  500 kHz

[0168] The various spread spectrum modes are utilized to obtain optimumperformance for particular modes of operation of the data terminal. Theradio of the present invention preferably has a transmission range of upto 300 feet for closely spaced interior surfaces and up to 1300 feet inopen spaces resulting in an operational coverage area from 280,000 to5,300,000 square feet.

[0169] Utilization of the various transmissions modes results invariable immunity of the data signals from RF interference. The dataterminal in which the radio is utilized thereby has the ability toextract the best system performance in every application regardless ofmultipath signal levels, interference levels and the sources thereof.The data terminal also thereby has the ability to dynamically trade datarate in return for coverage range (coverage range being a function ofprocess gain) without the need to change radio hardware. Although notshown, capable of operating in the 2.4 GHz circuitry of FIG. 10 or otherfrequency ranges. Multiple intermediate frequency filter topology may beimplemented to achieve interference rejection via varying filterselectivity.

[0170] MODES 1 and 3 are full band direct sequence and provide no inbandinterference protection other than high process gains of 18.7 dB and15.7 dB respectively. Out-of-band protection from cellular transmissionsoperating in the vicinity is provided. MODE 1 provides good coveragearea and rejection of multipath signal. MODE 3 provides shorter coverageare in return for a high speed data rate.

[0171] MODE 2 is a channelized direct sequence mode having a processgain of 17 dB. A single direct sequence cordless telephone operating inthe vicinity will not degrade performance on at least four of thechannels. MODE 2 provides a reasonable coverage area and jammeravoidance with channelization.

[0172] MODE 4 utilizes full band frequency hopping having a process gainof 17.1 dB. A single direct sequence cordless telephone will not degradeaverage throughput by more than 10 percent. MODE 4 provides moderatecoverage area and high system capacity with dynamic jammer immunity withfrequency hoping.

[0173] MODE 5 is a direct sequence mode which is frequency hopped havinga process gain of 37 dB. A single direct sequence cordless telephoneoperating in the vicinity will not degrade average throughput by morethan 10 percent. MODE 5 provides a long and high coverage area anddynamic jammer immunity with frequency hopping in return for a low datarate.

[0174] MODE 6 is an on-off-keying (OOK) modulation mode having a processgain of 0 dB. MODE 6 may be utilized as a low speed, low power link to anearby scanner or printer for example.

[0175] MODE 6 the transceiver module is intended to communicator withperipheral devices containing simple AM transceivers. The Main VCO isset to the center frequency of the peripheral AM receiver. For OOKtransmission, the data formatter is configured to produce a CW outputsignal. OOK signaling is providing by strobing the enable line on thetransmitter, shown in FIG. 16.

[0176] For OOK reception, the Main VCO is set to receive at the AMtransmitter center frequency. The RSSI output from the limitingamplifier is used for AM detection. The signaling rate is limited by thespeed at which the A/D can quantize the RSSI (preferably samplingseveral times per symbol), and at which the MAC μP128 can process thesampled data to extract the modulation.

[0177] MODE 7 is a channelized direct sequence mode having a processgain of 20 dB. A single cordless telephone operating in the vicinitywill not degrade performance on more than nine of the channels.

[0178] Other modes may also be included other than those listed above.Other possibly included modes may be variations or new combinations ofthe above modes or modes utilizing different modulation techniques andfrequencies such as other standard RF transmission techniques which maybe contemplated by the present invention. For example, an additionalmode in an alternative embodiment may include voice communicationstransmissions utilizing standard audio modulation techniques achieved byswitching channels or transmissions modes. Using voice communicationsthe transceiver module may allow data terminal operators of amulti-level radio-frequency communications network to verballycommunicate with one another or their supervisors throughout the entirenetwork. Voice and data communications may be utilized with a singleportable battery powered electronic device rather than having a dataterminal for data communications and a separate mobile radio for voicecommunications, for example. Similarly, the process gains, samplingrates, etc., are exemplary value which may be modified as provesdesirable.

[0179]FIG. 11 is a conceptual block diagram of the operation of thetransmitter of FIG. 10 when operating in a direct sequence spreadspectrum transmission mode. As illustrated, in the operation, data isreceived by the BASE BAND FORMATTER/SPREADER which, based upon theCONTROL SPREADER signal received from the MAC μP 128, spreads the codebased upon a particular code spreading sequence or pattern. The BASEBAND FORMATTER/SPREADER provides data on two output paths so that thedata may be modulated according to the BPSK modulation scheme. Thespread code is then processed by a programmable transversal filter 150having two separate filters, 146 and 148, one for each data path. Oncefiltered, the data is modulated by the components 136, 138, 140, 320,and 142 of the BPSK modulator. From the BPSK modulator, the dataproceeds until it is transmitted.

[0180]FIG. 12 shows a conceptual diagram of the operation of thereceiver utilized in conjunction with the transmitter of FIG. 11. In theembodiment, data received by the antenna 112 passes through azero-degree phase shift block 152. From the block, one path goesdirectly to one input of a multiplier 158 while the second path passesthrough an RF DELAY block 154 and then passes to a second input of themultiplier 158. DELAY CONTROL is supplied to the RF DELAY block 154 bythe MAC μP 128 dependent upon the frequency of the received signal tocause a desired phase shift. From the multiplier 158 the signal passesthrough a baseband data filter 160 then through X² block 162 prior toits furthered processing.

[0181]FIG. 13 is a block diagram of the receiver 114 of the presentinvention. The receiver 114 may be located on the radio card CCA 44 ofFIGS. 7, 8 and 9. Wideband filter 170 provides additional interferenceprotection in the narrow band modes. A preselector filter 164 receivesan RF data transmission signal from the antenna 112 (not shown). Thepreselector filter 164 may be a two pole bandpass filter (BPF) designedto have a wide bandwidth to keep the insertion loss low. In an exemplaryembodiment filter 164 has a center frequency of 915 MHz, a bandwidth of26 MHz and an insertion loss of 3.5 dB. However, the filter 164 could becontrollable as well based upon desired filtering characteristics.

[0182] The output of the preselector filter 164 is fed into two lownoise RF amplifiers (LNA) 166 and 168 each of which preferably has again of 10 and a noise figure of 2.2 dB. The gain of the RF amplifies166 and 168 is sufficient to overcome any noise which may be present onthe input RF data signal. The amplified signal may be sent to a bandpassfilter (BPF) 170 for additional preselection filtering. Bandpass filter170 is preferably designed to have four poles to provide high stop bandrejection of possible signal images present in the data signal, havingdesign values of 915 MHz center frequency, bandwidth of 26 MHz and aninsertion loss of 3.5 dB. Bandpass filter 170 could also be controlledto provide desired filtering characteristics.

[0183] The output of filter 170 is sent to the input of a mixer(“MIXER”) 170 which mixes the data signal with the output 332 from themain voltage controlled oscillator of the frequency generator circuitry116 of FIG. 10 which preferably has an output frequency of 844 MHz. Theoutput of the mixer 172 is passed through an additional bandpass filter174 having a center frequency of 71 MHz, a 26 MHz bandwidth andinsertion loss of 2.0.

[0184] The data signal is passed through an intermediate frequencyselectable bandwidth filter 322 comprising filters 174, 176 and 178 forsignal path 180, which varies the filtering of the data signal accordingto the various modes of operation. Bandpass filter 176 is utilized forMODE 2 operation and has a bandwidth of 5 MHz and an insertion loss of 8dB. MODES 1 and 3 utilize a direct signal path 180 with an overallbandwidth of 26 MHz from the output of filter 174. MODES 4, 5, 6 and 7utilize bandpass filter 178 which has a bandwidth of 500 kHz and aninsertion loss of 8 dB. Multiple intermediate frequency filtertopologies may be implemented to achieve interference rejection viavarying filter selectivity.

[0185] The data signal is fed into an intermediate frequency amplifier(IF) 182 to overcome the losses from the filters. The IF amplifier 182is a high gain amplifier having a gain and a noise factor of 7 dB. Theoutput of the IF amplifier 182 drives the demodulator 181 which alsoreceives the output from the auxiliary voltage controlled oscillator ofthe frequency generator circuitry 116 of FIG. 10 which may operate at afrequency of 142 MHz. The demodulator 184 may have data signal productsI and Q which are fed into the inputs of the despreader circuitry 120 ofFIG. 10. The receiver 114 may have a noise figure of less than 7 dB, animage rejection figure of 60 dB and adjacent channel rejection of 40 dB.

[0186]FIGS. 14A and 14B are diagrams illustrating the operation of thepseudo-random number generator circuitry (“PN GENERATOR”) 122 of thetraverse filter 150 of FIG. 10. The pseudo-random number generatorcircuitry 122 is preferably located on the radio interface card 58 ofFIGS. 7, 8 and 9. The pseudo-random number generator 122 produces apseudorandom binary output which is mixed with the data signal code inorder to minimize the rate distortion for a given number of bits used torepresent the data signal. The PN generator 122 may be comprising an8-bit shift register (“8-BIT SHIFT REGISTER”) 186 utilizing a feed backselector control (“FEEDBACK SELECT”) 188 which provides programmablefeedback. A restart control device (“RESTART CONTROL”) 190 may beutilized to provide a programmable restart interval and a programmablerestart vector. The PN generator 122 is preferably controlled by acontrol input (“CONTROL”) from the MAC circuitry 128 of FIG. 10 andproduces a PN code output signal (“PN CODE”).

[0187] In the frequency hop (FH) mode, data is converted to an I/Qformat for minimum shift keying (MSK) modulation. Narrowband modulationis preferably employed so the spreader function may disabled. The powerspectral density of MSK modulation exhibits a main lobe bandwidth ofapproximately 1.5 times the symbol rate, but also contains substantialenergy in the side lobes. This energy might create interference to otherin-band or out of band systems and may also degrade operation if severalfrequency hopping sequences are used for increased throughput ormultiple access. To reduce side lobe energy, transversal filtering isemployed in the I/Q modulation paths. These consist of shift registersclocked at the symbol rate or a multiple thereof. The digital outputsfrom the shift registers are summed using a weighted resistor ladder(350 and 352) is external to the ASIC and constitutes the interfacebetween digital and analog processing.

[0188] In the direct sequence (DS) modes, the data is mapped into I/Qsymbols for either BPSK or QPSK modulation. The ASIC generates asynchronous chip clock at a multiple of the symbol rate that is appliedto the pseudo-random number generator 122 to produce a chipping sequenceat the selected spreading ratio. The exact chipping sequence is selectedby programming the feedback select 188. The chipping sequence ismultiplied with the I/Q data symbols by use of exclusive OR gates (324and 326). The selected data rate and spreading ration determine the mainlobe bandwidth of the transmitted signal. The bandwidths of the mainlobe and side lobes are reduced by applying the transversal filters (146and 148) with the shift registers operating at the chipping rate ratherthan the symbol rate. The main lobe bandwidth is preferably limited toapproximately 1.6 times the chip clock frequency.

[0189]FIG. 15 is a block diagram illustrating the frequency generatorcircuitry 116 of FIG. 10. The frequency generators 116 are preferablylocated on the radio card CCA 44 of FIGS. 7, 8 and 9. The radiointerface card 58 of FIGS. 7, 8 and 9 may provide data signals (“DATA”,“CLOCK”, “STROBE” and “LOCK DET”) 190 and a clock signal (“CLOCK”) 192which is preferably a 30 MHz clock to the fractional number frequencyagile synthesizer (“FRACTIONAL N SYNTHESIZER”) 194. The 30 MHz clocksignal may be divided to produce frequencies of which 30 MHz is amultiple. The synthesizer 194 may also receive frequency input signalsfrom a main voltage-control oscillator (MAIN VCO) 196 and from anauxiliary-voltage controlled oscillator (AUXILLARY VCO) 198. Thesynthesizer 194 preferably switches between transmission and receivingmodes in 200:s or less.

[0190] The main VCO 196 preferably operates at a nominal frequency of844 MHz while the auxiliary VCO 198 preferably operates at a nominalfrequency of 142 MHz. The synthesizer 194 has loop filter feedback paths200 and 202 to oscillators 198 and 196 respectively for control of thefrequency of the outputs of the oscillators 196 and 198. The main VCO196 supplies a signal to the down converter mixer 172 of the receiver114 of FIG. 13 and provide a signal to the modulator 206 of thetransmitter 118 of FIG. 11 after being fed through a divide by 2 circuit(“DIVIDE BY 2”) 204.

[0191]FIG. 16 is block diagram illustrating the functionality of thetransmitter circuitry 118 of FIG. 10. The transmitter 118 is located onthe radio card CCA 44 of FIGS. 7, 8 and 9. The transmitter 118 receivesdata signal input products I and Q from the modulator and spreadercircuitry 124 and 130 of FIG. 10. The transmitter input data signal Iand Q are mixed with the output of the auxiliary VCO 198 of FIG. 15which are then combined and mixed with output of the main VCO 196 ofFIG. 15 using an up converter mixer in the transmitter modulator 206.

[0192] The output of the transmitter modulator 206 is preferably fedinto a high pass filter (HPF) 208 having the data signal below thenominal carrier frequency of 900 MHz for single side band (SSB)transmission. The output of the high pass filter (BPF) 210 whichpreferably has a counter frequency of 915 MHz and a band width of 26MHz. The output of bandpass filter 219 is fed into two amplifier (AMP)214 preferably having a gain of 20 and a second amplifier (AMP) 214preferably having a gain 30 to provide the necessary transmission outputpower. The power of the data signal at the output of amplifier 214 isnominally at least 1 watt which is fed through a lowpass filter (LPF)216 and a bandpass filter (BPF) 218. Because of the insertion losses ofthe filters 216 and 218 of 0.7 dB and 3.3 dB respectively, thetransmitter 118 has a nominal output power of at least 250 mW which istransmitted via antenna 112 of FIG. 10.

[0193]FIG. 17 illustrates the circuitry for selecting between the modesof modulation of the present invention. In frequency hopping mode thecorrelator (“CORRELATOR”) 330 us bypassed and the decision and timingrecovery block (“DECISION TIMING RECOVERY”) 332 performs MSK detection.An alternative approach would be to use an FM discriminator, a functionthat is commonly available in limiting amplifier IC's. This is possiblebecause MSK signal are known to be capable of demodulation as either FMor PSK signals.

[0194] In DS modes the correlator 330 preferably extracts the datasymbols from the chipping sequence. The decision and timing recoveryblock 332 outputs send the recovered data (“DATA”) and a clock signal(“CLOCK”) to the MAC μP 128 for frame processing.

[0195]FIG. 18 is a block diagram of the MAC circuitry 128 of FIG. 10.The MAC circuitry 128 is preferably located on the radio interface card58 of FIGS. 7, 8 and 9. The medium access control circuitry 128 may beutilized in the protocol of communications media used in a particularcommunications network. The media access circuitry 128 may also utilizethe 2.4 GHz MAC protocols to provide operation on both 9000 MHz and 2.4GHz networks.

[0196] The media access protocol may be controlled by a MACmicroprocessor (“MAC μP”) 224 which receives a timing control signalfrom a crystal oscillator (“XTAL”) 246. The MAC microprocessor 224 maycommunicate with the electronic device in which the radio of the presentinvention is to be utilized via a host communications bus (“HOST”). TheMAC microprocessor 224 may further have input and output signals 248from an analog-to-digital converter (“A/D”), digital-to-analog converter(“D/A”), an electrically erasable read only memory (E²ROM”) or a resetcontrol circuit (“RESET”) for example. The MAC microprocessor 224 mayutilize random access memory (“RAM”) 250 which may be either volatile ornonvolatile memory. The MAC microprocessor 244 may also receive an inputfrom OTP 252. A control bus (“CONTROL”) is utilized to control thecircuitry of the radio card 44 of FIGS. 7, 8 and 9.

[0197] The MAC microprocessor 244 may have registers to read the statusof and control the functions of the radio interface card 58. Registersmay also be provided to control the transmission power state of theradio of the present invention. The MAC microprocessor 244 may provide aparallel-to serial converter for control and programming of thesynthesizer 194 of FIG. 15. Additionally, the MAC microprocessor 224 mayprovide a programmable periodic timer, clock control of the CPU of thedata terminal 10 and PCMCIA programmable clock generation.

[0198]FIG. 19 is a block diagram illustrating the host interfacecircuitry 132 of FIG. 10 for radio module 30 of FIG. 7 and forradio/scanner module 20 of FIG. 8. The host interface circuitry 132 ispreferably located on the radio interface card 58 of FIGS. 7 and 8. Aregulator (“REGULATOR”) 254 functions as the power supply 134 of FIG. 10and provides a regulated voltage signal to the radio interface card 58which is connected to the MAC circuitry 128 via a host to MACcommunications bus (“TO MAC”) which connects to the electronic device inwhich the radio of the present invention is utilized through connectors(“CONNECTORS”) 60 on the radio interface card 58 of FIGS. 7 and 8.Further connection is made to a buzzer (“BUZZER”) circuit 256 which maybe the buzzer 64 of FIGS. 7 and 8. A bus connection to the radio/scannermodule 20 of FIG. 8 is provided for control of the scanner 258 which maybe a laser scan engine (“LASER SCAN ENGINE”).

[0199]FIG. 20 is a block diagram illustrating the host interfacecircuitry 132 of FIG. 10 for PCMCIA radio module 42 of FIG. 9. ThePCMCIA radio module host interface circuitry 132 is preferably locatedon the radio interface card 58 of FIG. 9. A FET switched power supply(“POWER SUPPLY FET SWITCH”) 260 functions as the power supply 134 ofFIG. 10 and provides a supply voltage output (“TO RIC”) to the radiointerface card 58 of FIG. 9. A microcontroller (“μC”) 262 providesinterfacing signals (“TO MAC and PCMCIA CONNECTOR”) between the MACcircuitry 128 of FIG. 2B and the electronic device in which the radio ofthe present invention is to be utilized through PCMCIA connectors 102 ofFIG. 9.

[0200]FIG. 21 is a diagram illustrating an alternate configuration ofportable data terminals according to the present invention.Specifically, a communication network 1450 provides an overall networkenvironment for portable data collection terminals 1454. A host computer1451 is connected to access points 1452 via a wired connection 1453. Theaccess points 1452 are in turn communicatively coupled to portable datacollection terminals 1454 via wireless links 1455. The wireless links1455 may be one or more of a plurality of wireless communicationstechnologies, including narrowband radio frequency, spread spectrumradio frequency, infrared, and others.

[0201] A dock 1456 and a portable data terminal 1458 according to thepresent invention may be connected to the wired backbone 1453, and mayserve a function similar to an access point 1452. The dock 1456 mayprovide power to the terminal 1458, or alternatively the dock may beabsent and the terminal 1458 may run for a limited time under the powerof its battery. The terminal 1458 connects directly to the wiredbackbone 1453, and also communicates with another terminal 1454 througha wireless link 1455. The terminal 1458 may, for example, be equippedwith protocol converter circuitry to convert communication on the wirebackbone 1453 into wireless communication on the link 1455, and also toconvert wireless communication on the link 1455 to a format forcommunication on the wire backbone 1453. The communication moduleassociated with terminal 1458 thus improves the versatility of theterminal 1458.

[0202]FIG. 22A illustrates one embodiment of the data collectionterminal of the present invention, having both wired and wirelesscommunication capability. A data terminal 1500 is shown having acommunication module 1502 and a base module 1504. The communicationmodule 1502 contains a wired transceiver 1506, a wireless transceiver1508, and processing and interface circuitry 1510. The base module 1504contains a control processor and interface 1512, an applicationprocessor 1514, and terminal circuitry 1516 containing data input anddisplay portions and other circuitry well known in the art. The blocksshown in communication module 1502 and base module 1504 are simplifiedfor exemplary purposes, and it will be understood by one skilled in theart that a data terminal 1500 according to the present invention is notlimited to the block circuitry shown in FIG. 22A. In another embodiment,the communication module 1502 may contain additional transceivers forcommunicating on other mediums and in other networks. The processing andinterface circuitry 1510 of the communication module 1502 isolates thecircuitry of the base module 1504 from the differing operatingcharacteristics of the transceivers, so that communication by any of thetransceivers can be accommodated by the circuitry and software routinesof the base module 1504.

[0203] In operation, the processing and interface circuitry 1510 of thecommunication module 1502 is programmed with the network configurationto route communication through either the wired transceiver 1506 or thewireless transceiver 1508. An incoming message on the wired transceiver1506 may be routed and processed to a terminal display portion, or maybe routed to a host computer, a dock, or another portable data terminal1500 through the wired transceiver 1506 or through the wirelesstransceiver 1508, whichever is appropriate. Similarly, an incomingmessage on the wireless transceiver 1508 may be routed to display orthrough the wireless transceiver 1508 or through the wired transceiver1506, whichever is appropriate for the destination. By provided for therouting functions to be done in the communication module 1502, the powerused in the base module 1504 can be minimized. Specifically, theinterface with the control processor 1512 and the application processor1514 need not be used, which allows the main terminal in the base module1504 to remain dormant while communications are routed in thecommunication module 1502.

[0204] The choice of which transceiver to use in routing communicationis based on a “least cost” analysis, considering factors such as thepower required to send the message through a particular transceiver, thespeed at which the message will be received from a particulartransceiver, the possibility of error associated with each transceiver,etc. A wired connection is usually selected when available, but routingdecisions may vary with the different characteristics of each messageand the mobility of the terminal. The processing and interface circuitry1510 in the communication module 1502 is preferably capable ofperforming the least cost routing analysis for all communicationmessages, without activating any processing power from the base module1504.

[0205]FIG. 22B is a diagram illustrating a specific implementation ofthe portable terminal of FIG. 22A a single PCMCIA card contains not onlya multi-mode wireless transceiver, but also a wired modem transceiver.In particular, a portable terminal 1520 contains terminal circuitry 1522comprising processing circuitry 1526, conventional terminal circuitry1528 and interface circuitry 1530. The interface circuitry 1530 providesa PCMCIA interface for receiving PCMCIA cards of various functionality.The terminal circuitry 1522 is well known and can be found inconventional portable or hand held computing devices.

[0206] Via the interface circuitry 1530, the portable terminal 1520accepts PCMCIA cards. As illustrated, the PCMCIA card insertedconstitutes a communication module 1524 which provides both wired andwireless access. Specifically, the communication module 1524 comprisesprocessing circuitry 1532, a multi-mode wireless transceiver 1534 (suchas set forth previously), a wired modem transceiver 1536 and interfacecircuitry 1544. When in use, the wired modem transceiver 1536 interfacesvia a jack 1540 to a telephone line (not shown). Similarly, the wirelessmulti-mode transceiver 1534 communicates via an antenna 1538.

[0207] Whether the modem transceiver 1536 or multi-mode transceiver 1534is being used, the processing circuitry 1526 always delivers andreceives data and messages via the interface circuitry 1530 in the samemanner and format, i.e., the interface circuitry 1530 supports a commoncommunication interface and protocol. The processing circuitry 1532 ofthe communication module 1524 receives data and messages via theinterface circuitry 1544. If the modem transceiver 1536 is being used,the processing circuitry 1532 appropriately (de)segments and(de)compresses the data/messages utilizing a digital signal processor(DSP) 1542. Otherwise, the processing circuitry 1532, including the DSP1542, participate to assist in wireless communication via the multi-modetransceiver 1534. Thus, the module 1524 not only saves on PCMCIA slots(as required when a conventional radio card and a conventional modemcard are both being used), but also saves costs and increasesreliability by sharing common circuitry resources. In particular, themodem and multi-mode transceivers 1536 and 1534 share the interfacecircuitry 1544 and processing circuitry 1532 which includes the DSP1542.

[0208]FIG. 23 is a diagram illustrating the use of portable terminalsaccording to the present invention utilizing both wired and wirelesscommunication in a network configuration. Specifically, a server 1515 isshown connected to mobile computing devices (MCDs) 1554 via a wiredcommunication link 1552. The communication link 1552 may alternativelybe an infrared link, or another communication technology. MCDs 1554 areconnected to each other and to the server via the link 1552. MCDs 1554are also communicatively coupled to each other via wireless links 1556.

[0209] The network involving the server 1550, the communication link1552, and the MCDs 1554 represents a primary communication network, thatis preferable to use when there are no interference or disconnectionproblems in the network. The network between MCDs 1554 involvingwireless links 1556 represents an auxiliary or backup network, which isused where there are problems with the primary network, or to rundiagnostics on the primary network. The MCDs 1554 are equipped toautomatically switch from the primary network to the auxiliary networkwhen a problem arises on the primary network. This network redundancyallows the MCDs 1554 to remain in constant communication with each otherand with server 1550.

[0210] For example, a wired network on a communication link 1552 doesnot recognize connection well, and may not immediately detect a loss ofconnectivity. MCDs 1554 utilize wireless links 1556 to diagnose a lackof connection on the wired network 1552. For example, an MCD 1554 mayactivate its radio to send a test message to another component of thenetwork, either another MCD 1554 or the server 1550, to testcommunication on the wired link 1552 by sending a reply test messageback to the inquiring MCD 1554. The test routine is preferablyimplemented and controlled by the processing/interface circuitry 1510 inthe communication module 1502 (see FIG. 49) of the MCD 1554. If thereply communication test is not received, the MCD 1554 will know thatthere is a problem on the primary network, and will inform other MCDs1554 to switch to the auxiliary network. The MCDs 1554 can continue tocheck the primary network via wireless links 1556 until the primarynetwork is back in service.

[0211] Some MCDs 1554 may be out of range to effect wirelesscommunication with server 1550 by a wireless link 1556. An out-of-rangecondition is determined according to the particular communication andconnection protocol implemented by MCDs 1554 and other networkcomponents such as server 1550. In this situation, the out-of-range MCD1554 sends its message, along with an out-of-range condition indicator,to another MCD 1554 that is in communication with the server 1550, andthe in-range MCD 1554 forwards the message on to the server. Similarly,the server 1550 sends its messages intended for the out-of-range MCD1554 to an in-range MCD 1554 to be forwarded over a wireless link 1556.The MCDs 1554 are capable of automatically switching from the wirednetwork to the wireless network and vice versa for each communicationattempt.

[0212]FIG. 24 is a diagram illustrating the use of portable dataterminals according to the present invention utilizing both wired andwireless communication to access separate subnetworks in an overallcommunication network. Specifically, a wired network includes wiredserver 1600 and mobile computing devices (MCDs) 1606 connected by awired communication link 1604. MCDs 1606 are also part of a wirelessnetwork with wireless server 1602, and are communicatively coupled toeach other and the wireless server 1602 via wireless communication links1608. Wireless links 1608 may be radio frequency communication links,such as narrowband, direct sequence spread spectrum, frequency hoppingspread spectrum or other radio technologies. Alternatively, wirelesslinks 1608 may be infrared communication links, or other wirelesstechnologies. In another embodiment, the wired server 1600 and the wiredcommunication links 1604 may utilize infrared communication technology,with the wireless communication links 1608 being radio frequency links.The present invention contemplates various combinations of communicationtechnologies, all accommodated by communication modules of MCDs 1606.The communication modules of MCDs 1606 include any number oftransceivers operable on any number of communication mediums, since thedifferences in their operating characteristics are isolated from thebase module of the MCDs 1606 by a communication processor. The MCDs 1606are preferably able to automatically switch between the wired andwireless networks, controlled primarily by a communication processor intheir communication modules.

[0213] Some MCDs 1606 may be out of range to effect wirelesscommunication with wireless server 1602 by a wireless link 1608. Anout-of-range condition is determined according to the particularcommunication and connection protocol implemented by MCDs 1606 and othernetwork components such as wireless server 1602. In this situation, theout-of-range MCD 1606 sends its message, along with an out-of-rangecondition indicator, to another MCD 1606 that is in communication withthe wireless server 1602, either over a wireless link 1608 oralternatively over a wired link 1604 if both MCDs 1606 are constituentsof a wired network. The in-range MCD 1606 then forwards the message onto the wireless server 1602 over wireless link 1608. Similarly, thewireless server 1602 sends its messages intended for the out-of-rangeMCD 1606 to an in-range MCD 1606 to be forwarded over a wireless link1608 or a wired link 1604, if both MCDs are constituents of a wirednetwork.

[0214]FIG. 25a is a block diagram illustrating an embodiment of thepresent invention wherein a wireless access device uses a dedicatedcontrol/busy channel to manage a plurality of modes of communicationwith roaming terminals. Specifically, a wireless access device 1701manages communication in a cell of network with a plurality of wirelessterminals, such as a wireless terminal 1703. The network may contain aplurality of other cells each managed by an associated wireless accessdevice to provide site or premises wide ubiquitous wireless coverage forthe plurality of stationary and roaming wireless terminals. Asillustrated, for example, the network may also contain wiredcommunication links therein as provided, for example, by a wiredEthernet backbone LAN 1705.

[0215] The wireless access device 1701 comprises control circuitry 1711,a multimode transceiver 1713, an Ethernet transceiver 1715 and anantenna 1717. The Ethernet transceiver 1715 supports communicationbetween the backbone LAN 1705 and the control circuitry 1711. Similarly,the multimode transceiver 1713 supports communication into a wirelessnetwork cell to wireless devices within range such as the wirelessterminal 1703 via the antenna 1717. The multimode transceiver 1713 ismore fully described below in reference, for example, to FIG. 1C.

[0216] A wireless terminal 1703 also comprises a multimode transceiver,a multimode transceiver 1721, as well as an associated antenna 1723 andconventional terminal circuitry 1725. Using the multimode transceiver1721 and associated antenna 1723, the wireless terminal 1703communicates with the wireless access device 1701 when it is withintransmission/reception range.

[0217] The wireless access device 1701 selects (and may periodicallyreselect) one of a plurality of communication modes and associatedparameters of operation based on a variety of factors mentionedpreviously such as recent success rate, RSSI, neighboring celloperation, etc. However, when the wireless terminal 1723 roams withinrange of the wireless access device 1701, the roaming terminal mustidentify the currently selected mode and associated parameters beingused by the wireless access device 1701 to maintain the cell'scommunication. Although the wireless terminal 1703 could be configuredto scan each available mode to identify the currently selected mode andparameters, such efforts often prove time consuming.

[0218] Instead, the wireless terminal 1703 and wireless access device1701 are preconfigured with mode and parameter information that definesa default, busy/control channel. Thus, upon roaming into range of thewireless access device 1701, the wireless terminal 1703 first switchesto the busy/control channel by operating the multimode transceiver 1721according to the preconfigured mode and parameters, and then beginslistening. Within a predefined maximum time period thereafter, thewireless terminal 1703 will receive transmissions from the wirelessaccess device 1701 identifying the currently selected communicationchannel mode and associated parameters. The wireless access device 1701periodically broadcasts such information on the busy/control channel tocapture terminal that happens to need communication channel definitions(e.g., selected mode and parameters) to participate. The wirelessterminal 1703 utilizes identified mode and associated parameterinformation to switch the multimode transceiver 1721 over to theselected communication channel and begins participation thereon.

[0219]FIG. 25b is a drawing illustrating advantageous operation of thewireless access device of FIG. 25a when configured to handle hiddenterminal conditions. In particular, each of wireless terminals 1751 and1753 is configured to only switch from the busy/control channel (havingpredefined mode and associated parameters) to the communication channel(selected by a wireless access device 1755) when there is a need foraccess to the communication channel and the communication channel isclear (available). In this configuration, when no desire to communicateis present, the terminals 1751 and 1753 need only occasionally check thebusy/control channel to identify any outstanding messages orcommunication requests as transmitted by the wireless access device1755. If either terminal 1751 or 1753 desires to participate on thecommunication channel (to initiate communication or to respond toawaiting messages or communication requests), that terminal need onlymonitor the busy/control channel long enough to identify a clearcommunication channel before switching over to the communication channelto participate. As before, the wireless access device 1755 alsoperiodically identifies the communication channel mode and associatedparameters as selected and reselected by the wireless access device1755.

[0220] To fully appreciate this process, first assume that the wirelessterminals 1751 and 1753 are not within range of the wireless accessdevice 1755. Upon wandering within range of the wireless access device1755, the wireless terminal 1751 utilizing the predefined mode andparameters begins listening for transmissions on a busy/control channel.Within some time period thereafter, the wireless access device 1755participates on the busy/control channel to transmit: 1) the currentlyselected communication channel definition (i.e., mode and parameters);2) pending message and communication request indicators; and 3) currentchannel conditions. After identifying a need to participate, thewireless terminal 1751 awaits a transmission from wireless access device1755 (on the busy/control channel) that the selected communicationchannel is clear (not in use). When the channel is clear, the wirelessterminal 1751 adopts the selected communication channel definition andbegins participating thereon.

[0221] Second, assume that, while the wireless terminal 1751 is engagedin ongoing communication with a computing device 1761 on a backbone LAN1763 via the wireless access device 1755, the wireless terminal 1753comes within range of the wireless access device 1755 and desires toparticipate on the currently selected communication channel. Thewireless terminal 1753 adapts itself to participates on the busy/controlchannel and identifies, in periodic transmissions from the wirelessaccess device 1755, that the communication channel is busy. Thus, thewireless terminal 1753 must monitor the busy/control channel to identifywhen the communication channel is clear before adapting to thecommunication channel to participate.

[0222] This operation works whether or not the terminals 1751 and 1753are within range of each other. In particular, the terminal 1751,terminal 1753 and access device 1755 have transmission rangesillustrated by dashed circles 1771, 1773 and 1755, respectively.Although both terminals 1751 and 1753 are within range of the accessdevice 1755, neither are in range of each other and, thus, are referredto as “hidden” from each other. The access device 1755 is within rangeof both of the terminals 1751 and 1753. If the wireless terminal 1753attempted to transmit on the communication channel while the terminal1751 was transmitting, a collision would occur at the wireless accessdevice 1755. However, this is not the case because both of the terminals1751 and 1753 must receive a communication channel clear indication onthe busy/control channel from the wireless access device 1755 that is inrange of both, avoiding the hidden terminal problem. When participationis completed on the communication channel, the terminals 1751 and 1753readopt the busy/control channel definition (i.e., mode and associatedparameters).

[0223] Participation by the wireless access device 1755 on thebusy/control channel need only be by transmitting, although receivingmight also be employed in case the busy/control channel is to be shared.Similarly, participation by the wireless terminals 1751 and 1753 needonly be by receiving transmissions, although transmitting might also beemployed. In particular, transmission might be employed by a wirelessterminal on the busy/control channel if the wireless terminal does notsupport the currently selected communication channel, i.e., does notsupport the mode and associated parameters.

[0224] In addition, should the two terminals 1751 and 1753 be withinrange of each other and desire to intercommunicate, the wireless accessdevice 1755 will allocate an unused, non-competing mode in which the twoterminals can exchange information or data. In particular, one of thewireless terminals 1751 and 1753 first attempts to establish an exchangeby gaining access to the communication channel (via busy/control channelmonitoring). Once access has been established, the wireless terminal,e.g., the terminal 1751 delivers a request for poll message (RFP) to thewireless access device 1755 which identifies the amount of data orinformation to be exchanged if known, the recipient or target (e.g., theterminal 1753), and characteristics of the data or information such aswhether real time dedicated bandwidth is not needed, desired orrequired. If the amount of data or information to be exchanged isminimal and requires no dedicated bandwidth, the wireless access device1755 will not bother attempting to dedicate a mode to the transceivers1751 and 1753. Instead, the wireless access device 1755 will merelyrelay the information or data received from the terminal 1751 to theterminal 1753 and vice versa. Otherwise, the wireless access device 1755will examine its lookup table to see if the terminal 1753 currentlyparticipates within the network cell (i.e., within range) of thewireless access device 1755. If the terminal 1753 doesn't participate,the wireless access device 1755 will inform the terminal 1751 and onlyproceed with relaying functionality (or spanning tree wireless routing,for example) per confirmation by the terminal 1751. However, if theterminal 1753 does participate, the wireless access device 1755concludes that there is a good chance that the terminals 1751 and 1753are within range of each other. Thus, the wireless access device 1755attempts to identify an available and appropriate mode and associatedparameters that may be temporarily assigned to the terminals 1751 and1753 for their communication exchange. The wireless access device 1755attempts to communicate such channel information to both of theterminals 1751 and 1753. Thereafter, as soon as either of the terminals1751 and 1753 receive the information, the terminal will immediately settheir multimode radio to the dedicated mode and parameters, listen forpolling messages from the other terminal, and, if no poll messages aredetected, begin transmitting polling messages to the other terminal. Ifa polling message is received, the communication exchange, such asdedicated voice bandwidth, will take place. Afterwards, the terminals1751 and 1753 inform the wireless access device 1755 that the allocatedchannel is no longer needed and may be reallocated. Similarly, if aterminal polls for the other for a predefined period of time on theallocated channel without receiving any response, that terminal willinform the wireless access device 1755 of the failure, and the wirelessaccess device will free the allocated mode for reallocation orcommunication channel use.

[0225]FIG. 25c is a flow diagram illustrating the functionality of oneembodiment of the wireless access device of FIG. 25b in managing acommunication channel using a second channel, i.e., the busy/controlchannel. The wireless access device maintains ongoing communication orotherwise waits in an idle state at a block 1781. If a predeterminedtime out period (e.g., a B/C service time period) lapses while theaccess device is in an idle state as indicated at a block 1782, theaccess device switches to the predefined mode and associated parametersof the busy/control channel at a block 1783. At a block 1784, on thebusy/control channel, the access device transmits: 1) the currentlyselected communication channel definition (mode and parameters); 2)channel status indications; and 3) pending message/communication requestindications. Thereafter, at a block 1785, the access device switchesback to the selected communication channel mode and parameters, resetsthe B/C service time period (at a block 1786) and returns to the block1781 to participate on the communication channel.

[0226] If, while participating on the selected communication channel atthe block 1781, a request for poll (RFP) transmission is received from awireless terminal as indicated at an event block 1787, the wirelessaccess device responds by switching to the busy/control channel at ablock 1788 to deliver communication channel definition, channel “busy”indications and any pending message/communication request indications ata block 1789. Although the busy indication may only indicate that theselected communication channel is not available, it also indicates anestimated amount of time during which the channel will be busy. Thewireless access device derives this estimate from the overall data sizeto be transferred as determined from the data itself or from a field inthe RFP transmission, if known. This way, a waiting wireless transceivermay go to sleep while an ongoing exchange is taking place and wake upwhen the exchange is scheduled to have finished.

[0227] Thereafter, at a block 1790, the wireless access device switchesback to the selected communication channel mode and parameters, resetsthe B/C service time period (at a block 1791), transmits a Poll or Datamessage (whichever is appropriate under the circumstances) on thecommunication channel at a block 1792, and returns to the block 1781 toawait a Data or Ack (acknowledge) message from a participating wirelesstransceiver. In particular, in response to an RFP from a participatingwireless device that has Data to deliver via the wireless access device,the wireless access device delivers a Poll message at the block 1792 tothe participant, prompting for the Data. Otherwise, if the RFP indicatesa desire by the participating wireless terminal to receive Data, thewireless access device sends the Data at the block 1792. The Data sentat the block 1792 may be of any length including dedicated bandwidth foran unknown duration. Thus, if a wireless terminal listens for a periodof time greater than the B/C service time period and detects notransmission from the access device on the busy/control channel, thewireless terminal concludes that the selected communication channel isbusy.

[0228] Alternately, data may be segmented into Data packets fortransmission one packet at a time via the blocks 1781 and 1787-92. Inthis way, a listening wireless terminal will can be sure that it willreceive a communication channel broadcast via the blocks 1782-86 betweeneach Data packet transmission. Upon receipt, wireless terminals mayplace their transceivers in a sleep mode until each of the Data packetsof the data have been exchanged, and the communication channel is clear.

[0229] Upon receiving the data (or Data packet) or an acknowledge (ACK)message indicating successful receipt of data (or a Data packet) asindicated at an event block 1793, the wireless access device broadcastsa Poll, Ack or Clear message or sends data (or packets thereof) asproves appropriate at a block 1798. The access device then switches tothe busy/channel at a block 1794 to transmit the currently selectedcommunication channel definition, busy or clear indications and pendingmessages/requests at a block 1794. Afterwards, the wireless accessdevice switches back to the communication channel at a block 1796,resets the B/C service time period at a block 1797 and returns to theblock 1781 to continue communication exchanges or enter an idle state ifthe exchange is complete.

[0230]FIG. 26a is a block diagram illustrating an alternate embodimentof that shown in FIG. 25a wherein a wireless access device uses aseparate transmitter for the dedicated control/busy channel and aroaming terminal uses either a shared multimode transmitter or amultimode transmitter and a separate busy/control channel receiver. Inthe previous embodiments of FIGS. 25a-c, the wireless access device andwireless transceivers each used a multimode transceiver to supportparticipation on two wireless channels: the selected communicationchannel and the busy/control channel. As illustrated, this need not bethe case. Instead, a wireless access device 1801 participates using tworadios when communicating with a wireless transceiver 1803 (having onlya single multimode radio) and a wireless transceiver 1805 (having tworadios). With a dual radio configuration, participation on both channelsmay occur at the same time, increasing overall performance in manycircumstances.

[0231] In particular, a wireless access device 1801 comprises controlcircuitry 1811, an Ethernet transceiver 1813, a busy/control transmitter1815 and corresponding antenna 1817, and a multimode transceiver 1819and corresponding antenna 1821. Having separate radio units andantennas, the wireless access device 1801 participates on: 1) a selectedcommunication channel defined by mode and parameter information,servicing data exchanges in the communication network cell; and 2) thebusy/control channel defined by predetermined mode and parameterinformation known to all wireless transmitters, controlling access tothe selected communication channel. Such participation is oftensimultaneous, preventing a wireless terminal from having to wait long onthe busy/control channel for a transmission.

[0232] In one configuration, where hidden terminals prove to be oflittle concern, the wireless terminals 1803 and 1805 are only forced towait on the busy/control channel until they receive the selectedcommunication channel definition. In another configuration, as betterexemplified in FIG. 26b which follows, all wireless terminalsparticipate on the busy/control channel except when they have a need andgain access to the selected communication channel. In this latterconfiguration, when the wireless access device 1801 is participating onthe selected communication channel with the wireless terminal 1805, forexample, the wireless access device 1801 concurrently deliverscommunication channel definition, busy/clear status and message/requestindications on the busy/control channel. Such information can berepeatedly transmitted at any time interval desired or may betransmitted continuously.

[0233] Similarly, although a wireless transceiver may operate with asingle multimode radio as described previously, it may also takeadvantage of multiple radios. Specifically, the wireless transceiver1803 comprises terminal circuitry 1831 and only one radio, a multimodetransceiver 1833. Thus, the wireless transceiver 1803 is forced to timeshare participation on the busy/control channel and the selectedcommunication channel—often all that is needed. However, the wirelessterminal 1805 comprises terminal circuitry 1845 and two radios, abusy/control channel receiver 1847 and a multimode transceiver 1849. Assuch, the wireless terminal 1805 may place the multimode transceiver1849 in a low power state, and only powering up its busy/control channelreceiver 1847 to check in. Characteristics of the busy/control channelmay be chosen to permit significant overall power savings and simplicityin the design of the receiver 1847.

[0234]FIG. 26b is a drawing illustrating advantageous operation of thewireless access device of FIG. 26a when configured to overcome thehidden terminal conditions. As with FIG. 25b, the range of a wirelessaccess device 1911 is defined by a dashed circle 1913. Similarly, thewireless terminals 1915 and 1919 have ranges defined by dashed circles1917 and 1921, respectively. The wireless terminals 1915 and 1919 areout of range of each other. The wireless access device 1911 is withinrange of each of the wireless terminals 1915 and 1919.

[0235] Unlike the wireless access device 1755 (of FIG. 25b), thewireless access device 1911 participates on both a busy/control channeland a selected communication channel simultaneously. The wireless accessdevice 1911 delivers all communication channel information eithercontinuously or periodically on the busy/control channel, while idle orservicing any wireless terminal on the communication channel. By doingso, the wireless access device 1911 is free to set any length datasegments or none at all on a selected communication channel, whiledelivering communication channel information as often as desired on thebusy/control channel. Thus, the busy/control channel and communicationchannel can be designed for optimized performance without having toconsider time sharing of a single channel or time sharing a transceiver.

[0236] Thus, the busy/control channel can be designed to minimize thelistening time of the wireless terminals 1915 and 1919 to gain statusinformation. Sleep periods of the wireless (and often hand-held andportable) terminals 1915 and 1919 increased saving critical batterypower. Similarly, data segmentation can be set based solely on theconditions of the selected communication channel, and not merely toguarantee the wireless access device 1911 a maximum interleaving timeperiod during which the wireless access device 1911 will participate onthe busy/control channel.

[0237]FIG. 26c is a flow diagram illustrating the functionality of oneembodiment of the wireless access device of FIG. 26b in managing acommunication channel using a control/busy channel with dual radios.Specifically, a wireless access device waits in an idle state or isengaged in ongoing communication on the selected communication channelat a block 1951. As soon as a B/C time period lapses as indicated by anevent block 1953, the wireless access device branches to a block 1955 totransmit mode, parameter and status information regarding the currentlyselected communication channel along with indicators of pending messagesand communication requests. Afterwards, the wireless access deviceresets the B/C time period at a block 1957 and branches back to theblock 1951 to continue servicing the selected communication channel orreenter an idle state. Thus, a preset (B/C time period) intervals, thewireless access device delivers the selected communication channelinformation on the busy/control channel. The B/C time period may beconfigured to either minimize transmission overhead or minimize wirelessterminal listening times. The B/C time period might also be set to zero,causing the wireless access device to continuously transmit the selectedcontrol channel information (i.e., the selected mode and parameters,busy or clear status, predicted duration of a current exchange, andpending messages and communication requests). The B/C period is thus asynchronous period. Thus, a maximum value of the B/C period (or an othercommonly known value) provides a wireless terminal with a guaranteedmaximum listening time.

[0238] Although the B/C time interval may prove sufficient tocommunicate updates to the selected communication channel information,the wireless access device is also configured to immediately identifyany mode or parameter changes of the selected communication channel. Inparticular, at a block 1961, if for any of a variety of reasons thewireless access device decides to switch the mode and/or parameters ofthe communication channel, the wireless access device vectors toimmediately deliver such information on the busy/control channel via theblocks 1955 and 1957. Similarly, the wireless access device may also beconfigured (as indicated by the dashed lines) to respond to immediatelyreport status changes such as whether a message or a request fordedicated bandwidth has been received as indicated at a block 1963 andthe blocks 1955 and 1957. Other immediate event servicing may also beadded and similarly serviced.

[0239] Unlike the single radio (shared) embodiments previouslymentioned, the wireless access device services the block 1955 and 1957no matter what the wireless access device is currently engaged in on theselected communication channel.

[0240]FIG. 27 is a block diagram illustrating further embodiments of thepresent invention wherein channel selection and operating parameters aredelivered by a wireless access device on a dedicated busy/controlchannel with or without multimode transceiver capabilities. Inparticular, supporting a plurality of wireless terminals such as aterminal 2013, a wireless access device 2011 maintains two channels: acommunication channel and a busy/control channel as previouslydescribed. To carry out such functionality, the wireless access device2011 may comprise control circuitry 2021, an Ethernet transceiver 2023and either a single, configurable transceiver 2025 (for operating onboth the communication and busy/control channels) or a singletransceiver 2025 (for the communication channel which may have onlylimited if any configuration capability) and a single transmitter 2027(for operating on the control channel).

[0241] With the single, configurable transceiver 2025, the wirelessaccess device may operate identically to that described in reference toFIGS. 25A-C. However, the configurable transceiver 2025 may not providemultimode operation, but only support multiple channels operating in asingle mode. For example, the transceiver 2025 may only support the modeof channelized direct sequence. Although only a single mode isavailable, the parameters such as (and defining) spreading codes,spreading code lengths, channel center frequency and channel bandwidth,for example, alone, and without mode change, provide the wireless accessdevice 2011 with the ability to support a dedicated busy/control channeland provide a plurality of other channels for maintaining thecommunication channel.

[0242] Alternatively, the wireless access device 2011 may also comprisea dedicated busy/control transmitter 2027. If it does, the wirelessaccess device 2011 with a multimode transceiver 2025 would operate asdetailed in reference to FIGS. 26A-C. If configured with a single modetransceiver 2025 supporting only one channel, the wireless access device2011 would still maintain the communication and busy/control channelsbuy need only identify parameter and pending messages and communicationrequests on the busy/control channel. Of course the busy/control channelwould still solve the hidden terminal problems and provide theassociated benefits described above. Finally, with the transmitter 2027supporting the busy/control channel, the transceiver 2025 might supportmultiple communication channels without supporting multiple modes ofoperation. In such configurations, the wireless access device 2011 neednot report mode change information on the busy/control channel.Reporting all other information and aforementioned control would stilltake place.

[0243] The wireless transmitter 2013 could accommodate the same wirelessconfiguration as described in reference to the wireless access device2011. Along with conventional terminal circuitry 2029, it may have amultimode or non-multimode, configurable or non-configurable transceiver2031. The transceiver 2031 might operate independently or utilize asupporting busy/control receiver 2033. Lastly, although not necessary,the transmitter 2027 and receiver 2033 might each constitutetransceivers.

[0244] As is evident from the description that is provided above, theimplementation of the present invention can vary greatly depending uponthe desired goal of the user. However, the scope of the presentinvention is intended to cover all variations and substitutions whichare and which may become apparent from the illustrative embodiment ofthe present invention that is provided above, and the scope of theinvention should be extended to the claimed invention and itsequivalents. It is to be understood that many variations andmodifications may be effected without departing from the scope of thepresent disclosure.

1. A communication network for collecting and communicating data,comprising: a wireless access device comprising a control circuit and afirst RF transceiver that selectively operates in one of a plurality ofspread spectrum modes; at least one mobile terminal comprising a secondRF transceiver that operates in at least one of a plurality of spreadspectrum modes; and the control circuit responsive to transmissionsreceived from the first RF transceiver for evaluating communicationperformance and dynamically selecting one of the plurality of spreadspectrum modes of the first RF transceiver while taking intoconsideration the at least one of the plurality of spread spectrum modesof the second RF transceiver.
 2. The communication network of claim 1wherein the plurality of spread spectrum modes of the first RFtransceiver comprising a direct sequence transmission mode and afrequency hopping mode.
 3. The communication network of claim 1 whereinthe plurality of spread spectrum modes of the first RF transceivercomprising a direct sequence transmission mode and a channelized directsequence mode.
 4. The communication network of claim 1 wherein theplurality of spread spectrum modes of the first RF transceivercomprising a frequency hopping mode and a hybrid frequency hopping mode.5. The communication network of claim 1 wherein said first RFtransceiver operates to support a communication channel and abusy/control channel on a time shared basis.
 6. In a communicationnetwork, a plurality of wireless access device capable of communicatingwith a plurality of wireless terminals, each of the plurality ofwireless access device comprising: a first radio controllable to supporta communication channel operating pursuant to one of a plurality ofmodes; a second radio supporting a busy/control channel independent ofthe communication channel; a controller that selects one of theplurality of modes and controls the first radio to support theselection; and the controller utilizes the second radio to communicateon the busy/control channel to manage the communication channel.
 7. Inthe communication network of claim 6, wherein the plurality of modesincludes a plurality of spread spectrum modes.
 8. In the communicationnetwork of claim 7, wherein the first radio comprises a multimode radioand the second radio comprises a transmitter.
 9. In a communicationnetwork, a plurality of wireless access device capable of communicatingwith a plurality of wireless terminals, each of the plurality ofwireless access device comprising: a transceiver controllable to operatepursuant to any of a plurality of communication modes; a controller thatselects from the plurality of modes a communication channel and anindependent, busy/control channel; and the controller controls thetransceiver to support data routing on the communication channel whilemanaging access to the communication channel via the busy/controlchannel.
 10. In the communication network of claim 9, wherein theplurality of communication modes includes a plurality of spread spectrummodes.